Editor: Terrain Selection
When in a terrain editing mode, selection mechanisms should be applied to the terrain. As usual primary select does set the selection and secondary select toggles the selection. The shape of the area affected by the selection change is defined by the state of the brush button.
Note that there will be different types of selections for texture tiles and vertices. Ideally selections should convert when switching from one edit mode to another.
(RM-3871 from redmine: created on 2017-05-14 by Marc Zinnschlag, )