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
Add method in StatModel class, to load from String

Added a method "loadFromString" which is based on the "load" one. It
allow to directly pass the XML string which can be usefull and faster
when you have a huge file in a variable.
Changing tabs to spaces.

Edited previous code to change tabs into spaces.
Re-editing Documentation

Attempting to re-editing the documentation, to satisfy buildbot error
status.
Re-edition of documentation

Re-edited the documentation again.
Remove unnecessary kercn limitation of 4.

When accessing global memory by DWORD4, memory bandwidth
can be fully utilized on Intel platform. This patch will
make more image format(e.g. 8UC4) be processed in DWORD4
by work-item. After applying this patch, 3 subcase of
./opencv_perf_core --gtest_filter=OCL_RepeatFixture_Repeat.Repeat/*
can be speedup on HD4000 graphics card with Beignet:
OCL_RepeatFixture_Repeat.Repeat/2, 64% improvement.
OCL_RepeatFixture_Repeat.Repeat/6, 50% improvement.
OCL_RepeatFixture_Repeat.Repeat/8, 56% improvement.

Signed-off-by: Chuanbo Weng <chuanbo.weng@intel.com>
Fixed whitespace warnings in new tutorials
Build separate world-like iOS framework for contrib
highgui: Support to change trackbar count in setTrackbarPos and replaced deprecated CreateToolbarEx in Windows.
Removed "FORMAT_XML" to generalize format

Removed the "FileStorage::FORMAT_XML" to generalize format of the String
model.
Reduce variables scope, move declaration to first use point
Merge pull request #3486 from Chuanbo-Weng:repeat-perf