The simulation controls are now grouped in a common panel, which is also collapsable. Also moved the 'Hide sidebar' button on top of the sidebar for a better user experience. This closes #36.
The icon type of newly created vertices is now determined based on the predominant type of icons used in the graph. This closes #33 (again).
Merge branch 'vladi' into develop

Conflicts:
	src/main/java/model/MyVertex.java
	src/main/java/view/CustomMouse/CustomPopupPlugin.java
Fixed error in merge
Fixed NPE when adding nodes to an empty graph