Added a libfreenect2_api export macro - to apply __declspec(dllexport) infront of all classes that is used from the library libfreenect2.

If they are not specified VS won't generate a .lib file and protonect will give linking errors.
Made a ifdef for packing data to work on windows also.
Added header files so they are visible in VS solution tree.
Added FindLibUsb and FindTurboJPEG cmake files, to search for the respective libraries, instead of hardcoding in a sub depend folder.

Only testet on windows.
to use max in VS <algorithm> needs to be included and <type> as to be used.
Merge branch 'libfreenect2packeddata'
Merge branch 'libfreenect2headers'
Merge branch 'libfreenect2FindLibs'
Merge branch 'libfreenect2mathfix'