Editor: Scene as drop target for textures
Dropping a texture asset record onto a scene should change the terrain texture. If the destination texture tile is not selected only this tile should be changed. If the destination tile is selected the whole selection should be changed.
This function should be available both in terrain texture editing modes and other editing modes. The availability in other editing modes needs to be controlled via a user settings option.
(RM-3869 from redmine: created on 2017-05-14 by Marc Zinnschlag, )