Icemap MapEnts

[rakiru]

This has 2 parts:

• New MapEnts chunk type for Icemap. This will store information about all entities in the map. This can include spawn points, pickup locations, prancing llama locations and preferred dance move, etc. It will be stored in a format similar to: {"ents": [{"class": "llama", "llama_type": "prancing", "dance_move": "Time Warp", "pos": [128, 32, 128]}]}
• Add common.map_ents_get and common.map_ents_set API methods to access the MapEnts info.

Known entity types should be documented as implemented, so tools can begin using them.

[rakiru]

Done in 48908935fea10924d8ad67b5b7caa7881a4e619f

[rakiru]

Derp herp, forgot to implement saving.