restore function beta test

A lot of time has passed, but now the beta test for the restore function has started. Here as usual big thanks to @Tylerjet, because he did almost everything on it. More information can be found in the related discussion. We look forward to your help with testing, suggestions and criticism about this milestone.

And what else?

Oh, and we've also added a little new feature:

• New function added: use_filenames_as_commit_msg (commit)
  • Optional: Now the changed files are displayed in the commit history instead of the timestamp. More information in the docs.
• Add GNU General Public License 3 (commit)