Revert "Don't allow fast forwards even on single commit branches." in favor of a config based solution.

This reverts commit f9eea3027c5cb4dd26f9c91f3f1e94cf162ffff4.
Ask if fast forward merges should always be prevented and save the answer to the config file.
Move the always no fast forwards option into a configuration file.
Merge branch 'feature/config_noff' into develop