render-order feature for map
Merge branch 'feature_renderorder' of https://github.com/digitalhoax/tiled into feature_renderorder

# By Lennert Raesch
# Via Lennert Raesch
* 'feature_renderorder' of https://github.com/digitalhoax/tiled:
  render-order feature for map

Conflicts:
	src/libtiled/orthogonalrenderer.cpp