Update segmentation.cpp

Added detailed comments to watershed()
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
Prevent division by zero
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.
White space and spelling in meanshift tutorial

Removed a leading whitespace from a parenthetical comment and corrected the spelling of "maybe"
Fixed typo in description of Rect operations
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.
Python test: added options to provide local data path
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>
Remove unnecesary operations and calculations in loop body.

Signed-off-by: Yan Wang <yan.wang@linux.intel.com>