Remove remaining gtk deprecation warnings

https://bugzilla.gnome.org/show_bug.cgi?id=737142
Removed deprecated gtk stuff code side

I walked the way through the *.py files and changed the deprecated stuff to some more up to date stuff

https://bugzilla.gnome.org/show_bug.cgi?id=737142
Remove unnecessary debug print
Remove additional deprecations

Forgot a few - and forgot to clean up after myself

https://bugzilla.gnome.org/show_bug.cgi?id=737142
Lookup's start_new_thread should also be inside try-catch
Find path in libmediaart response by searching for path

It seems that since libmeddiart 0.6 params are swapped,
 we should not rely on indexes and search for path instead

https://bugzilla.gnome.org/show_bug.cgi?id=737571
Set grilo plugin ranks to avoid extra last.fm calls

https://bugzilla.gnome.org/show_bug.cgi?id=736241
notifications: remove unused Gtk import
Replace start_new_thread with Thread class
albumArtCache: put album resolve threads in queue

The queue is being processed in two workers, each resolve thread is
being terminated if it takes more than 30 secs to finish

https://bugzilla.gnome.org/show_bug.cgi?id=732151