Relocate hamster.db to ~/.local/share/hamster-time-tracker

Created by: GeraldJansen

Revert from ~/.local/share/hamster-applet to ~/.local/share/hamster-time-tracker as default location for hamster.db. In the long run this will be less confusing given that all other installation directories now use hamster-time-tracker and not hamster-applet.

In this proposal, at first startup of hamster-service, if an existing database found under xdg_data_home/hamster-applet and not under xdg_data_home/hamster-time-tracker, a hard link will be created such that the two files are one and the same. That way if the user has an ongoing backup strategy in place using the hamster-applet directory, it will continue to work. At any time after first startup the old location can be deleted if desired (just the link will be deleted, the database will remain in the new location).