first shot at l2ork-style graph labels inside the graph

This fixes #590 (closed)

It also:

• reintroduces the awful "create array in last graph" dialog button because there's currently no other clear way to do such a thing.
• in the case of a multi-array graph, it will show little color rectangles as long as all the arrays aren't simply black.

Have a looksie:

Not too shabby!

Notice an obvious drawback, though: While of course multiple array names are difficult to read when placed inside the box, even a single array name is more difficult to read because data and label may overlap. That doesn't happen in Pd Vanilla.