Added: $GitPageFile variable. Set it to true if you want to keep
complete page files in git and not just text.
Fixed: previously git extension was chdir-ing into $GitRepo directory
without ever going back, this could have lead to problems if some other
code needed access to file system.
Fixed: now this extension will work smoothly if $DataDir is set to a
relative path.
Fixed: this extension was probably broken for wiki pages starting with
two dashes (e.g. --SomePage), this is now fixed by using -- to indicate
the end of command-line options.
Changed: GitCleanup is now using GitRun instead of backticks (like
everywhere else). It will also print the exit status of 'git commit'
command.
Changed: some tiny style improvements.
