Resource spawning

[PFQNiet]

Resources will be spawned as individual, infinite tiles. Each "node" will be a 3x3 square, and nodes can come in "fields" of several nearby nodes. Starting area will have Iron, Copper and Limestone - other resources will spawn elsewhere. Nodes will then be guarded by enemies.

Ore spawning can borrow ideas from RSO, and will be modified by world settings. Frequency works as normal, Size refers to number of nodes in a cluster, and Richness modifies the chances of impure/normal/pure nodes.

• [x] Remove vanilla ore spawning
• [x] Add custom ore spawning
• [x] Make ore spawning respond to map settings
• [x] Remove sulfuric acid as a requirement for Uranium (it will be part of refining instead)
• [x] Scale resources according to starting area size - coal shouldn't be too far, oil beyond that, caterium/quartz/sulfur after that, uranium/bauxite far out
• [x] Spawn some enemies near resources, except for starting area

[PFQNiet]

Progress so far: small biters spawn in the top-left corner of each node.
Still to do: vary up the enemies (spitters, crabs...) and that should also include actual handling of water-based nodes.