Pets Mod 0.7.4-26.1.x

Added code documentation and massively cleaned up the code.
- Added the Utils class, which contains a lot of helper methods that keep the jar much smaller.
Added official addon support, including a guide which can be found here.
- These addons add more pets into PetsMod. This was made out of:
  - A. Feeling that the mod would get too bloated if we kept adding a large amount of mods into the main mod.
  - B. Enabling users to create their own pets.