Equipment parsing

[biqqles]

This PR incorporates changes that:

• Rewrite formats/ini in a functional style, preparing the way for multithreading and pattern matching
• Define the full host of Equipment types and routines to create them
• Add new methods relating to markets to Base
• Correct my initial faulty understanding of how goods are linked to ships and equipment
• Tweak the Entity and EntitySet interfaces:
  • EntitySet.arb has become EntitySet.first
  • EntitySet.__repr__ now shows the class name
  • Entity.__getitem__ and __contains__ will now behave more sensibly with non-string types.