^ trees. added satMem feature!!

satMem is a member in the saturationEffect structure.
If true, then a material will keep its saturation long after the original saturating material has left the prximity of or material.
if false, then the saturation will be gone when the saturation material is gone.
fiddling with saturation. at this point, it is broken
+ satMem. ^ trees. ^ README. '%' MEANS BUG FIXES!

I added a "satMem" feature to saturation effects. now you can choose if saturations stick with materials over time or if saturations are only valid while the block is touching them.

upgraded trees.

updated the readme. it has better conventions now. now '%' means fixed bug.
^ M_material mas been changed to m_material. it is easier to type
Merge branch 'tree' of https://github.com/jensenr30/GridSim into tree

Conflicts:
	materials_and_cells.h