Use project version from Git

[ccomrade]

• Removed project version from CMake. Version is now based only on release tags (git describe).
• Unique short commit hash is included in version strings of non-release builds.
• Examples of new version strings:
  • v20 (release build)
  • v20-1-g1234567 (dev build with one commit since the last release)
  • v20-1-g1234567-dirty (dev build with one commit since the last release and local uncommitted changes)
• Added new Lua global variable CRYMP_CLIENT_STRING. The following version variables are available in Lua now:

CRYMP_CLIENT = 19
CRYMP_CLIENT_STRING = "v19-107-g3ed301a"
CRYMP_CLIENT_BITS = "64-bit"

• Removed problematic BUILD_DATE_TIME. It wasn't updated properly and violated rules of reproducible builds.