Doxygen tutorials: some fixes in RST-docs
Doxygen tutorials: basic structure
Doxygen tutorials: warnings cleared
Doxygen tutorials: cpp done
Doxygen tutorials: python basic
Doxygen tutorials: python final edits
User guide converted to doxygen
Doxygen tutorials: support contrib, some minor changes
Documentation: removed mention of Mat(IplImage*) constructor
Fixed whitespace warnings in new tutorials
Reduce variables scope, move declaration to first use point
Fix build for Android arm64-v8a
Merge pull request #3492 from Dmitry-Me:reduceVariablesScope1
Merge pull request #3479 from mshabunin:doxygen-tutorials
Merge pull request #3495 from taka-no-me:fix_android_arm64