Added Python setup docs for Ubuntu Machines (#10056)

clarify some passages, fix grammar errors

Corrected the Typo 'Hasing' to 'Hashing' in second item in Additional Resources section. Also added Wikipedia link for the LSH.

updated links for python, numpy and matplotlib

Fix grammar error in py_features_meaning.markdown (#8378)

0 corresponds to FLANN_INDEX_LINEAR

0 corresponds to FLANN_INDEX_LINEAR

Add initialisations to make clear what values actually have to be passed.

Moreover, in accordance with https://github.com/opencv/opencv/blob/383559c2285baaf3df8cf0088072d104451a30ce/modules/flann/include/opencv2/flann/defines.h#L68, I believe `FLANN_INDEX_KDTREE` was being initialised wrongly in the code examples, 1 should be correct, whereas 0 is `FLANN_INDEX_LINEAR`.

cv2.findContours() no longer modifies source image (#8150)

* cv2.findContours() no longer modifies source image

Since OpenCV 3.2, cv2.findContours() no longer modifies the source image but returns a modified image as the first of three return parameters.  ??? Do I have that correct ???

Also fixed up the code blocks to be valid markdown.

* ```python --> @code{.py}

Enables syntax highlighting in docs.

- disabled OPTIMIZE_OUTPUT_JAVA
- filtered out *.m scripts
- removed link to old Sphinx documentation
- replaced all mentions of Sphinx with Doxygen

Adding of destructor and placement new constructors for classes wrapped with CV_EXPORTS_W_SIMPLE macro

There were two bugs that were solved here.Changes were done after extreme testing.
1.replaced cv2.solvePnPRansac() with cv2.solvePnP() previous fc was giving terrible errors.
2.The code was incapable of saving edited pics;Now fixed with little code mods.

In the camera calibration code { cv2.cornerSubPix() } will be of no use.In the updated code it is assigned to the (corners2) variable 
which is passed down to { cv2.drawChessboardCorners() }