Text - Designer side by side

Since Qt Creator 2.8 a text eidtor can be dragged outside of the main window.

We did some smoke testing for 2.8 but for 3.0 this should really work.

Needs some testing and probably some performance optimizations.

Since optimizing the merging did fail I propose to use a timer including compression so the merging from text to designer happens only once in 200ms.

This should be enough to keep the text editor responsive.