Progression improvements and tilemap fixes

Forest Fellers

Forest Fellers! A game about Gnomes, Trees, and chopping them. Generate wood as you hire your very own Forest Fellers (Gnomes) to fell forests YOU make. Your Gnomes will grow and level up the more they chop allowing you to get more and more efficient trees for them to take down.

* Fixed desert tile map coverage * Fixed fall tile map coverage * Increased cost for some special gnomes to improve progression * Added a free tree button to save people from ruining their playthrough * Changed chance of rain to occur from 50% to 30% * Added arrow to back button so players are aware its a back button