+ fix: sqlite3.ProgrammingError: Cannot operate on a closed cursor on ProcessAlbumColors()
+ move processing artist images from periodic_scans to Populate
+ bump hash string limit from 7 to 10
+ add last_mod property to database
+ fix: TypeError: '<' not supported between instances of 'int' and 'str' on album page
+ use getters instead of constants in settings classes
+ refactor previous references
+ move get_xdg_config_dir() from settings.py to app.utils.xdg_utils.py
