Added chopped trees and other stuff

With this update I was inspired by a buddy of mine chopping down some of his trees in his game, so I started work on choppable trees.

The first ones I started one were the oak trees. All three oak trees can be chopped down now. I also started the long awaited low poly pass for the pine trees. There is now one low poly pine model. 

I also redid the low poly grass with a new version which should be more performant. 

I separated the fire logs and sticks so that you can use the logs and sticks individually.

Finally I made a couple more variants for the sleeping bag.