Use wikibase- as prefix for all messages

I've changed all the messages in client/ and lib/ to use wikibase-
as prefix as this makes moving them around and reusing them easier.
Furthermore I've moved 4 messages from the repo to the lib as I'll
need them on the client soon.

This is happening in cooperation with Raymond who will do the changes
I did for en here on TWN for all languages.

Change-Id: I5a013f5a2e6e11291428503bdc12dac07b9bd510
Merge "Use wikibase- as prefix for all messages"