notes on using dependency graph view

A little note on usage of the dependency graph (didn't get a chance to update docs yet):

a package fragment root (source folder) has to be selected and the metrics have to be
fully calculated. The view's drop down has a menu item for the dependency graph that
is now enabled. Red nodes and edges are part of cyclic dependencies, blue ones are not.
The reason the graph only works for source folders is that it displays package dependencies,
and a source folder selection is the only way to ensure they have all been calculated.

On windows the graph is displayed in a workbench view, on all other
platforms as a separate (AWT) window, as it is using the touchgraph library, and a
first attempt to port it to SWT was not very successful.
For more on this library, see : http://www.touchgraph.com