default.py: Add missed import
crunchy_json.py: Catch also urllib2.URLError
crunchy_main.py: Add context menu also for folders

Try to be useful by allowing to queue whole collections and add series
to Crunchyroll queue from everywhere where there is a single series as
target.

Also add menu items for addon settings and toggling debug mode.
Merge pull request #10 from Reinis/fix_menus

Fix menus