KCM KDED: Add immutability and fix default, reset, apply buttons
Summary:
- Reset and apply button are not activated anymore if we change twice state of an item going back to the current saved state
- Immutability disable all actions for an entry
- Default is activated if not all mutable entry are set to true
Reviewers: ervin, crossi, meven, broulik
Reviewed By: ervin
Subscribers: plasma-devel
Tags: Plasma
Differential Revision: https://phabricator.kde.org/D26784