Reenable translations after the KF5 port

- explicitly link to KI18n;
- set the application domain for the application (kio) and the libraries
  (plugins, kcm);
- use ki18n_wrap_ui instead of qt5_wrap_ui to enable translations for
  UI files;
- extract the message of the lame plugin (existing strings but not
  extracted for translation), fix a porting TODO.

CCMAIL: release-team@kde.org
CCMAIL: xiangzhai83@gmail.com