Added the expansion rendering code.
Checks for the expansions added to the drone and renders the model on
one of the available positions.
Put the init of all items, blocks, (tile)entities in their own class.
Started using reference class.
Changed name of mod class to ModularMulticopterDrones
Made some changes to the modules, now there are passive modules. As a
preparation to a chunkloading module.
Some work on pathfinding/movehelper, the drone was going one up before
moving to the next pathpoint under some vague circumstances.