Initial Windows RT support commit.
GPU module turned off;
TIFF support turned off;
Windows Managment and Video IO (VFW) turned off.
Multiple Windows RT fixes

TIFF build was fixed;
Direct Show back-end was enabled;
More accurate guards implemented.
More accurate guards for WinRT features in CMake.
Highgui tests for GUI disabled for WinRT;
Warnings fix;
Multiple fixes for WinRT

Fixed flann build with NEON;
Fixed Haming distance with NEON;
Honest cvRound for WinRT added;
cvRound test added;
Video IO with direct show disabled;
Video IO tests turned off for ARM WinRT.
HAVE_WIN32UI and HAVE_VFW checks and defines added.
Perf tests for Video IO on WInRT fixed.
Experimental MS Media Foundation API support added
Code review notes fixed.
Merge pull request #716 from asmorkalov:winrt