layer list now displays help text when no layers are added

Change-Id: I9b807407be64e4f9594abb94296055934e115775
Removed old PlotLayerEditor.

Change-Id: I93a594de0fb8e12c8921e7680c5390de69a41513
GUI cleanup.
Switched mx:ColorPicker to CustomColorPicker.

Change-Id: I2e96e6a578cc71534bdc42e33deca26283418a06