Small bug fixes and updates.

We realized the past build was a little crash-prone. So we've fixed that, and tweaked some small settings.

Changes

• Back-end optimization with object pooling and cacheing that should make the game run a little smoother
• Grass now does not grow at all during the Winter phase
• Amount of grass in grass patch reduced from 9 -> 5
• You can now properly enter a den while a worker is standing on top of it