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.
if i got this correct, ```isEmpty``` would be false, ```m_navigationHistory``` is null and accessing ```isLast``` would be a hard thing to do. so just exit the function first when ```isEmpty() || m_navigationHistory->isLast()``` and else, do stuff below.