* Created python version of the code for the anisotropic image segmentation tutorial. Created python/cpp toggles for the markdown file.

* fix doxygen warnings

enables Video I/O backend via Media NDK

When running with >1 OpenCV thread, KMeans index generation was
non-deterministic because of a RWW race. Issue is resolved by removing
the offending logic from the parallel section.

* Add Android Media NDK video i/o file capture back-end

* Fix failing test

* Improve error handling/prevent resource leaks

* Add license text

* Modify default for WITH_ANDROID_MEDIANDK option

* Fix spelling of deleter_AMediaExtractor

 * optimize v_lut_deinterleave
 * optimize v_interleave_/pairs/quads/triplets
 * optimize v_lut, use vec_extract instead of aligned store

keep it empty to avoid failures of these declarations:
static CV_CONSTEXPR const int var = ...;

Many of the Android samples rely on an options menu to work properly
but, at least on newer devices, the menu is permanently hidden by the
Android theme "Theme.NoTitleBar.Fullscreen", which means that most
of the examples were dysfunctional.

Allow nodes produced after some operation to be
"unused": not being an output and not being used
as inputs to other operations

Add fluid test to cover this case

The Android NDK 16b has a bug that sets the ANDROID_NDK_REVISION
variable incorrectly, generating an unexpected line break in the
middle of the string. This breaks the build as the generated
version_string.inc presents an invalid C string.

Remove leading and trailing line breaks, warns for line breaks in the
middle of 'msg' and escape them before appending to
OPENCV_BUILD_INFO_STR.