Plugin API Mega-Issue

[Naamloos]

As the server takes shape, I do somewhat feel like it may also be time to add more abstractions to the plugin API.

Here's a list of things we've gathered so far (prone to changes):

• World Provider Abstractions (e.g. a plugin can make an SQLWorldProvider)
• Overriding for Mob AI, or adding new variants (when Mob AI gets implemented)
• ProtocolVersion fo Plugins

Feel free to add suggestions!