kcmodule/profiles: QML port of the "Energy Saving" KCM

* Add SleepModeModel and PowerProfileModel in kcmodule/common
* Add ProfilesConfigKCM.{h,cpp} for the C++ backend KQuickManagedConfigModule
* Rebuild UI in QML, with the main tab contents in ProfileConfig.qml

After this, we'll be able to remove ActionConfig, EditPage and
action{config,edit}widget as well as all of the bundled ActionConfig
subclasses from the repository.