Fix waveform and overview graphics in Deere.

* Re-add marker PNGs.
* Move images to an image sub-directory.
* Fix colors / paths for Overview and Visual nodes.
Restore Deere traditional colors.

* Deck 1 and Deck 2 are blue and orange.
* Deck 3 and Deck 4 are violet and lime. (?)
* Start removing some of the debugging background colors.