issues/690: A new mode to allow live update of the grid while you edit the glyph.

It is fairly responsive on my 2600K with a minimal glyph. I've not tested with
more serious splinesets but on modern hardware it should hopefully be responive
enough. There might be some minor lag when dragging points around.

Many of the transforms also update in near real time :)
Merge pull request #770 from monkeyiq/2013sep/issues/690

issues/690: A new mode to allow live update of the grid while you edit the glyph.