2.1.5: improved grass and a new style preset

In this update:

• A new option to display "edge trees" is added (Display > Edge trees in the context menu).
• The road now cuts through "grassy hills" instead of going over them.
• The grass is drawn slightly differently now to make it subtler and at the same time more visible.
• Steps are now displayed as short grass stripes in the Glade view.
• A new style preset (for the Glade view) called Reef is added.