[Stellarium-pubdevel] Last StelModules done.

[<fab...@go...>]

Hi,
I finally finished to make StelUi and StelCommandManager real StelModule
(almost) managed as the other ones!
It is an important milestone toward version 1.0.0 because the soft is now
more modular, and the StelApp class is cleaner.

The only classes which are now strongly inter-dependent are StelUI and other
old ui-related classes, StelCommandManager, ScriptMgr, ImageMgr.
It is useless to try to clean them at this point because most of them are
going to disapear for 1.0.0.

Fabien