[popup] Change popup alignment relative to anchor

Which lets popup move under anchor istead of being
strictly attached to it (that was an effect of bottomcenter
for some reason)
(helps #40)
[prefs] Call onChange handlers with new value as first argument
[popup, preferences-popup] Option to hide zero content types

(close #60)
[locale] Update de-DE
Merge pull request #8 from futpib/master

Update my fork