KConfigXT for activities
Finally getting to the real meat of #23 (closed). Before getting into the larger change of porting power state profiles, this MR ports activity settings to KConfigXT.
No QML port of the activity power mangement KCM, but I'm simplifying the existing QWidget KCM further to only include two checkboxes per activity, no switch anymore between "Do not use special settings" and "Define a special behavior". Checking neither of the "inhibit X" checkboxes is synonymous to "Do not use special settings". The migrated config structure also reflects this simplification.
For reviewing convenience, this MR includes three separate, atomic commits:
- KConfigXT migration for activity behaviors
- Add tests for config file migration
- Use PowerDevil::ActivitySettings instead of KConfig
Note that GitLab lets you look at diffs from separate commits one at a time. They all come with individual commit messages, you can check those out before diving into the code. Thanks in advance for any reviews!