Inventory API

An official, better Inventory API.

- [x] Inventory
  - [x] Block Inventory
  - [x] Entity Inventory
  - [x] Equipable Inventory
  - [x] Merchant Inventory
  - [x] Inventory factory
  - [x] Custom inventory
- [x] Recipes
  - [x] Recipe general
  - [x] Shaped recipes
  - [x] Shapeless recipes
  - [x] Ore dictionary
- [x] Javadocs

Note that due to forge mod tinkering we cannot have the nice methods and grids and such that I was proposing and from bukkit. This is on the roadmap though.
We can probably fix this outside of the pr.