Added a new map with no enemies and fixed some issues

- Added a new map, Safe Lands. There are no enemies in this map and no wining or lose conditions
Playing this map in easy mode will use the summer tileset, in normal the autumn and in expert mode the winter.
- Added an sfx when you activate the windmill
- Fixed a gamepad issues when you go back to welcome screen
- Fixed a soft lock in The Siege, to build the trebuchet you now need to advance to the castle. It is no longer required that the trebuchet is inside the safe zone (between last wall and ground banner).
- Added a particle effect for farms when the windmill is activated.