API restricted on WinRT partially removed from core.

Additional CMAKE flag WITH_WINRT added.
TLS calls on WinRT replaced on variables with C++11 "thread" attribute.
WinRT API Certification fixes for core and contrib.
Warning and review notes fixes.

WITH_WINRT -> ENABLE_WINRT_MODE;
Some temporary char* replaced with Ptr<char>;
Build fix for regular WIN32;
Windows Platform SDK and MSVC search added to cmake;
Warinig fixes.
Added sample links in documentation for python2, ocl and gpu
Merge pull request #1205 from asmorkalov:winrt_api_cert_fix
Merge pull request #1214 from StevenPuttemans:feature_3169_others