Change path where marble will store data from /home/user/MyDocs/marble to /home/user...

Change path where marble will store data from /home/user/MyDocs/marble to /home/user/MyDocs/.local/share/marble. This comes closer to the original xdg default and prevents indexing by the tracker application and visibility in the file manager. No automatic migration, please move yourself if you have data lying around in the old location.