Use colors to group nodes after a pattern search

I've modified the viv UI to be able to change the color of a given group of nodes (CTRL+RETURN) while keeping the previous color in the other nodes. Up until now, every new search would highlight the matching nodes and reset the others to the default color.

I've also modified the title of the html window to show the name of the graph file. This is very useful if you are comparing graphs.

The end result would be something like this: