Cobblemon: Nests & Dens

New Content
- Fossil Nests - added to all rarity dens and allows the player a chance of finding a fossil
- Added Den portal rarity colours to help identify a dens rarity before entering (green = rare, orange = epic & purple = legendary)
- Nests have a low chance of producing a rare or epic eggs (can be disabled via config file)
- Added Scent Lure items, which can be used on den cores to help spawn a den of that rarity

Tweaks
- Increased the default rarity of both dens and nests
- Increased the length of time for a nest to get a new egg
- Increased the length of time for a den to reopen

Bug Fixes
- Fixed an issue where the den guardian spawns floating in the air
- Fixed the issue where the den guardian doesn't use the pokemon sleep animation (if available)