More closely follow the Semantic Versioning Specifications

I have removed all of the SVN related code in favor of Git.  By default this attempts to inject the git hash of the current commit at compile time.  If git is unavailable it looks for a .githash file in the root of the repo.  You can disable the git hash injection by using the --without-githash scons option to save on compile time (every git commit would cause all objects to be re-compiled).  Also added the pre-release versioning scheme as specified in SemVer.  All version information variables are still set in `<fife>/engine/core/version.h`.