Make The Code Robust Against Usage Of The "Save Project As" command

[maarzt]

The code (MastodonGitRepository) assumes in many places (save or relaodFromDisk) that projectModel.getProject().getProjectRoot() does not change and always points to the mastodon.project subfolder of the git repo. That is not the case. The only thing necessary to brake the assumption is to run "Save Project As" when using the Mastodon git tools.

The code needs to become more robust in this regard. ReloadfromDisk and save should always use the fixed path into the git repository and not rely on projectModel.getProject().getProjectRoot().