Reorganization

[Stivais]

Reorganized the project to be modular.

• World and Player now contains only the basic functionality for running a bare-bones server.
• Introduced WorldExtension and PlayerExtension traits to add custom functionality for the server. These traits are interdependant. Meaning, PlayerExtension must correspond to its WorldExtension, and vice versa.

This cleans up the mess inside main.rs, where all the ticking for the server, world, entities and players would happen.

• The dungeon struct now implements WorldExtension, where all ticking for it happens (mainly for rooms).
• Introduced DungeonPlayer, which handles ticking for an individual player.

Entities also received a minor rework.

• Reworked EntityMetadata to use a procedural macro to add serialization for a struct, so it matches Minecraft's Entity DataWatcher, without needing to hard code it.
• Added EntityAppearance trait, which handles when an entity enters/leaves a players view, allowing to spawn entities past a singular mob defined by the old metadata. Example of this usage can be seen in Door's EntityAppearance.

Minor changes include:

• Added Mort.
• Added Instant Transmission ability for AOTV.
• Added Tactical Insertion Item.
• Added optional Dungeon-breaker feature.
• Fixed chunks/entities not unloading properly.