Storage issues&external disc support

[Anrimian]

Allow to add external storages(add to folders toolbar menu option?) Place it in settings->library

Disappearing files: O1: do not delete file from catalog when it's not found? + storage analyzer: use fast insert approach to speed up first launch(if library size is 0 then insert all) O2: on storage event receive repeat scan after 5 seconds(if were remove changes)(on next event cancel delayed scan)