**1) Ctrl+Shift+F for file search**
Most text editors and IDEs (QtCreator, Visual Studio) have Ctrl+Shift+F to activate "Search in files".
Tasks:
- Remove current binding for Ctrl+Shift+F (Fullscreen)
- Bind Ctrl+Shift+F to "Search in files"
- Maybe bind Ctrl+Alt+F (currently "Search in files") to Fullscreen
2) Goal: Make (higher) F keys unbound by default
- TODO: describe details
- see also this Diff in progress: https://phabricator.kde.org/D17442