Tiled 1.0.3 released

It was found that Tiled 1.0.0 to 1.0.2 could crash on reloading a map, so upgrading to Tiled 1.0.3 is very much recommended. This release includes a bunch of other fixes as well, outlined below.

This is a companion discussion topic for the original entry at http://www.mapeditor.org/2017/08/29/tiled-1-0-3-released.html