Allow server to handle entity spawning

[dylanrenwick]

The main client scene should not have a player entity spawned by default.

Instead, when the player logs in, the server should spawn a player entity at the relevant location, and send that spawned entity to the client to be spawned in, along with other entities on screen.

• [x] Remove player entity from client
• [x] Create player entity prefab in client
• [ ] Create entity data class
• [ ] Create entity spawn packet
• [x] Spawn new player entity when player logs in on server
• [ ] Send new entity spawns to client via entity spawn packet
• [ ] Spawn new entity on client when receiving entity spawn packet

[dylanrenwick]

The client should maintain a collection of named entity types, similar to how tiles are handled. When the server sends an entity, it can include an entity name, which tells the client how to render the entity.

This includes not only what sprite(s) to use, but how to process animation. The server does not need to know anything about sprites or animation.