Remove unused variable
qt: Pick translation messages only from necessary files

Utility libraries (common, util) as well as extra tools shouldn't be
parsed for translation messages, only the server and wallet part qualify
here.
Move ui_interface to bitcoin_server.a

There is no need for it in the utility libraries or tools.
Put it in init.cpp, and in the tests separately (as they can't link init).
Merge pull request #4459

73ac7ab Move ui_interface to bitcoin_server.a (Wladimir J. van der Laan)
5090303 qt: Pick translation messages only from necessary files (Wladimir J. van der Laan)
Merge pull request #4467

1f740dd Remove unused variable (R E Broadley)