Replace obsolete qSort(), QSignalMapper, and child() with non-obsolete methods
Test Plan:
- Compile and install.
- Run Lokalize, try to insert proposals from TM, try to remove TM entries.
Reviewers: sdepiets, aacid
Reviewed By: aacid
Subscribers: aacid, Localization
Differential Revision: https://phabricator.kde.org/D23343