Added MSVC PCH support.

CMake macro from http://stackoverflow.com/questions/148570/using-pre-compiled-headers-with-cmake
CMakeLists.txt: Remove extra "+" from VERSION_STRING if VERSION_PATCH is set.
SADXModLoader: Added project version and git version.

Project versoin is set in CMakeLists.txt.

git version will only be added if POSIX sh is available.