While generating Java JNI wrappers package names with an underscore (`_`) character where not properly escaped according to https://docs.oracle.com/javase/8/docs/technotes/guides/jni/spec/design.html#resolving_native_method_names (see also: https://github.com/Itseez/opencv_contrib/issues/652).

This fix replaces all the occurrences of `_` with `_1` resulting in proper JNI method names.

They were issued for every frame retrieved - even in a release build.

* Adds the main features2d header to the parse list for the generator.
* Removes the manual definition of drawKeypoints and drawMatches since these are now included in the main header.
* Updates the generator to ignore SimpleBlobDetector, FlannBasedMatcher and DescriptorMatcher as these cause conflicts with the generator. This is okay since these were not previously included in the distribution anyway, so no harm is done.

refactored; added Camera2, notify callbacks, front/back maxCamera sizes; disable new stuff if target API < 21

Corrected typo and unused imports

a simple sample will look like:

```java
public class MainActivity extends Activity implements CameraGLSurfaceView.CameraTextureListener {

	CameraGLSurfaceView mView;
	ByteBuffer buf;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        requestWindowFeature(Window.FEATURE_NO_TITLE);
        getWindow().setFlags(WindowManager.LayoutParams.FLAG_FULLSCREEN,
                WindowManager.LayoutParams.FLAG_FULLSCREEN);
        getWindow().setFlags(WindowManager.LayoutParams.FLAG_KEEP_SCREEN_ON,
                WindowManager.LayoutParams.FLAG_KEEP_SCREEN_ON);
        setRequestedOrientation(ActivityInfo.SCREEN_ORIENTATION_LANDSCAPE);

        mView = new CameraGLSurfaceView(this, null);
        mView.setCameraTextureListener(this);
        setContentView(mView);
        buf = ByteBuffer.allocateDirect(1920*1080*4);
    }

    @Override
    protected void onPause() {
        mView.onPause();
        super.onPause();
    }

    @Override
    protected void onResume() {
        super.onResume();
        mView.onResume();
    }

	@Override
	public void onCameraViewStarted(int width, int height) {
		// TODO Auto-generated method stub

	}

	@Override
	public void onCameraViewStopped() {
		// TODO Auto-generated method stub

	}

	@Override
	public boolean onCameraFrame(int texIn, int texOut, int width, int height) {
		Log.i("MAIN", "onCameraFrame");
		int w=width, h=height;
		/*
		// option 1:
		// just return 'false' to display texIn on screen
		retutn false;
		*/

		/*
		// option 2:
		// fast copy texIn to texOut
		GLES20.glActiveTexture(GLES20.GL_TEXTURE0);
    	GLES20.glBindTexture(GLES20.GL_TEXTURE_2D, texOut);
		GLES20.glCopyTexImage2D(GLES20.GL_TEXTURE_2D, 0, GLES20.GL_RGBA, 0, 0, w, h, 0);
		return true;
		*/

		// option 3:
		// read, modify and write back pixels
		GLES20.glReadPixels(0, 0, w, h, GLES20.GL_RGBA, GLES20.GL_UNSIGNED_BYTE, buf);

		buf.rewind();
		// red line
		for(int i=0; i<h; i++) {
			buf.position(w*4*i+i*4);
			buf.put((byte) -1);
			buf.position(w*4*i+i*4+4);
			buf.put((byte) -1);
		}
		buf.rewind();

		GLES20.glActiveTexture(GLES20.GL_TEXTURE0);
    	GLES20.glBindTexture(GLES20.GL_TEXTURE_2D, texOut);
		GLES20.glTexSubImage2D(GLES20.GL_TEXTURE_2D, 0, 0, 0, w, h, GLES20.GL_RGBA, GLES20.GL_UNSIGNED_BYTE, buf);
		return true;
	}
}
```

fixing fourcc

Android: renamed default library name for static and dynamic fallback load; fixed libz import for 64-bit platforms

Revert of "Merge pull request #4006 from sgjava:opencv-steve" (reverted from commit 47431840)

Revert of "Merge pull request #4014 from sgjava:opencv-sgjava" (reverted from commit 52fa55a7)

Update android+AsyncServiceHelper.java

Update android+AsyncServiceHelper.java

changed tabs in last commit to spaces

Update android+AsyncServiceHelper.java

small formatting fixes

small formatting fixes

changed tabs in last commit to spaces

   (use "git reset HEAD <file>..." to unstage)

	modified:   highgui/include/opencv2/highgui/highgui_c.h
	modified:   highgui/src/cap_dshow.cpp
	modified:   java/generator/gen_java.py

The correction of the orthographic error in the enumeration constant
CAP_PROP_MONOCROME has been undone.

   (use "git reset HEAD <file>..." to unstage)

	modified:   modules/highgui/include/opencv2/highgui/highgui_c.h
	modified:   modules/highgui/src/cap_dshow.cpp
	modified:   modules/highgui/src/cap_pvapi.cpp
	modified:   modules/java/generator/gen_java.py

Änderungen in der PvAPI hinzugefügt.

   (use "git reset HEAD <file>..." to unstage)

	modified:   modules/java/generator/gen_java.py
	modified:   modules/videoio/include/opencv2/videoio.hpp
	modified:   modules/videoio/include/opencv2/videoio/videoio_c.h
	modified:   modules/videoio/src/cap_dshow.cpp
	modified:   modules/videoio/src/cap_pvapi.cpp

Following changes have been made:
1. Some minor bugs have been removed.
2. In the PvAPI module the option CAP_PROP_MONOCROME has been removed because
   this option does not make sense and causes an error if a color camera is used.
3. Instead the new option CAP_PROP_PVAPI_PIXELFORMAT has been added which allows
   to activate the different pixel formats (color modes) of an AVT camera.
4. Since there were two identical defines
   CAP_PROP_MONOCROME = 19
   CAP_PROP_MONOCHROME = 19
   which were also used in the other module DSHOW, the first one with an orthographic
   error has been removed in favor of the second one.

1) Fixed deadlock if camera is started and stopped immediately
2) Invalid pattern usage of Object.wait(). Refer to "spurious wakeup": http://docs.oracle.com/javase/8/docs/api/java/lang/Object.html#wait
3) Fixed buffer usage:
  a) fix eliminates processing of zero NV12 (green in RGB) first frame
  b) latest ready frame is delivered for processing (not previous)