ref #135 Navigation/history

* Adds a history for cgsee navigation. 
* Supports all implemented manipulators and static presets. 
* Adds a gui widget to visualize all saved steps with a small thumbnail.
accessing one of the predefined matrices is most likely done to change the current view. we trigger an `onNavigated()` event to check if the viewmatrix has changed or not and only save a history element if it indeed has changed.

But that said, I just noticed all these methods call `frontview()` and therefore call `onNavigated()` twice. Improved this in c4a0041.