Ice content

edit : I see that the merge is failing, but I am too tired to find out why. I will look into this tomorrow.

Content mod aiming to add more content relating to low temperatures. Science labs were only a beginning.

This mod will be a long term project, but there have been some infrastructure changes that I want to get rolled into the main game to avoid code duplication. The only gameplay impact this PR should have is that monsters are slowed by the in game temperature. No items should spawn nor should any new tiles be visible.