Cache tags used in a library
Currently, the used tags in a library can only be displayed as soon as the items in a library get loaded. If a user has more than one library, than this leads to the problem that in the library selector a user first has to enter a library before the tags in it can be displayed.
It hence would be better if the tags used in a library would be cached so after a restart the tags would still be accessible without loading items upfront.