Rework version number management

[meekee7]

The OpenTrespasser.exe binary has a manifest containing the executable version. Its content can be viewed via the file properties in Windows Explorer. This information can also be extracted by tools and scripts.
Currently, the version indicated in the manifest is based on data hardcoded in gblinc\Version.hpp.

The following improvements are proposed:

• The version number is currently the same as vanilla Trespasser without the patch. It should instead be the OpenTrespasser version.
• The version string should include the shortened Git hash.
  • A CMake script should generate a header file that contains the shortened Git hash.
  • It remains to be decided if the script should run only during CMake generation or during every compilation.
• Ideally, all generated EXEs and DLLs should have a version manifest.