Control panel: preparation for update1

Some improvments to control panel application and de-info:
-------- de-info ---------
1. Simplified de profiles (now in most cases fully declarative)
2. Added in place documentation for de profiles
3. Added DE_CONFIG_APP field for seting desktop environment main configuration application

------ control panel -------
1. Added button for launch desktop related configuration app (near the desktop selection dropdown). 
If DE has configurator that app will be launched on click.

NOTE: This is for Edge only. Work is unfinished. Please merge this to edge only if control panel  on production will be stable (till this moment edge and production realization should be the same). 

TODO:
This is only first part of upcoming changes. I plan to review all of control panel items. Some dead items may be fixed or removed (like cups web ui). But also I plan to add almost all DE related items (for example almost all of KDE control center items). Also I plan to add ability to show/hide DE related items.