Started making build / testing easier in windows,

Added FindOpenCL macro to recognize OpenCL SDK and require OpenCL headers for build.
Added info about NVIDIA SDK problems. Should be compiled with Intel SDK.
Fixed one compile problem with Visual Studio 2013.
Added python implementation of xxd unix tool.
Fixed rest of the Visual Studio 2013 express compiling problems.
Fixed test bench to find bash and other tools from Git/bin

Fixed testbench to work also when there are spaces in source tree directory names.
Simplified Visual Studio compiling instructions and updated how to select OpenCL library to use.
Fixed shared library compilation to not add dllexport defines in non windows platform.