more elaborate handling of viewpoints for Scene creation

[anhi]

Reported by akdehof on 27 Feb 43349775 14:56 UTC The handling of different view points and camera positions should be much more elaborate to allow for easy creation of PresentaBALL lessons. Preferably we get a widget similar to the representation window, where easy activation/switching, storing and renaming of "views" is handled.

Such functionality is needed for our RTFact integration as well as PresentaBALL.