use builtin fp() for firepy
ignore if cover update fails because of removed artist/album
show new albums on dashboard by Track.created
ignore tag edits for watchdog

or we'll get multiple library processes doing the same thing and weird
things happening.

also improved watchdog debug logging some
don't move non-track files if it's a dir with tracks

read comment in code for more info
remove "leftover" opmuse.txt from dir

e.g. if it's the only file in a dir (not including subdirs)