Add 'compatibility bundles' to allow runtime library upgrades. #879
During the review of #865, it was found that we didn't have as much control over the libraries that CraftBukkit includes and plugins may depend on. After discussion, it was decided that Glowstone needs to have some control over updating these libraries. So, after much thought, I came up with the concept of the Compatibility Bundle.
These bundles are a collection of libraries that are statically compiled into our code. These libraries will be downloaded alongside any libraries specified in the config. In order to avoid conflicts, only one compatibility bundle will be allowed to be specified. In cases where there's a conflict between the user specified libraries and the compatibility bundle, the library from the bundle will be used and a warning will be issued to the console.
Other changes included: