Refactored the vertex icon related code.
Some housekeeping
WIP: partial support for saving the predominant icon style when it is changed so that it can be applied if the graph is cleared. Currently this is hardcoded.
Merge branch 'vladi' into develop

Conflicts:
	src/main/java/edu/uci/ics/jung/graph/MyGraph.java
More merge errors
Fixed bug where the type (human/computer) of the vertices in a graph would be lost if the graph is cleared, and then reset to Human by default.