finished the mountain height transitions
added flat height transitions
refactored the transitions plugin to use the first element of the terrain stack as terrain instead of calling a map method
refactored the debug plugin to use the first element of the terrain stack as terrain instead of calling a map method
introduced a layer class to simplify map layer handling
refactored the terrain separator to require the map and not to extend the renderer plugin base
refactored the terrain separator to serve as height provider
removed the height provider plugin
refactored the map to use layers
refactored plugins and renderer to use the layers
added a test for the parse map command
added a test for the maprender command
removed deprecated code