Fixed git-auth.bat for Windows

GITAUTH_BIN is now not set to the Batch file, but the Python command to run
the configuration file. Since msysgit runs a Cygwin(-like ?) Bash program for
the git hooks, it can not directly execute Batch files, and I had problems using
cmd /c.
Added git_auth.pattern module for Pattern matching with variable expansion
Added git_auth.pkgdata module and git_auth/pkgdata/ folder with update hook
Added git_auth.util.filemd5() and ~.rmtree(), also fixed, ~.make_posixpath()
Complete restructure of authentication interface, updated commands

- BaseAuthLayers now contains three core interface methods, one to determine the
general user privileges, the access rights to a repository and the update permissions
to a specific git ref
- The RestrictedAuthLayer has been updated, it can now manage three types of rules
that will allow advanced user management. It applies pattern matching and cascading
rules for huge flexibility. closes #3
- The user privileges are retreived from the authentication layer once from Shell.main()
and stored in Shell.user_privs now
- Shell.validate_repo_name() now returns an adjusted repository name, or returns
None if the repository name was invalid
- Implemented that the update hook is now copied to the bare git repository with
the ``repo init`` command (closes #4)
- A new default option ``repo_check_integrity`` was added (closes #6)
- Commands have been simplified in the implementation and now operate
more unified in their behavior and output