[freeciv-ai] rfc: ai properly evaluate governments

["Per I. Mathisen" <per@xxxxxxxxxxx>]

This is a very rough version of a minimalist patch for AI evaluation and
change of government. It removes more code than it adds, and yet, it
properly evaluates all government types (even modpack ones), sets techs
appropriately and changes to the best form of government.

The AI usually desires Democracy most of all, and Republic after that.
This is a usual list:

2: a govt eval Despotism: 1811
2: a govt eval Monarchy: 3356
2: a govt eval Communism: 3811
2: a govt eval Republic: 4811
2: a govt eval Democracy: 5763

But sometimes, especially when the AI has lots and lots of units in the
field, it can value Communism(/Monarchy) higher than Republic/Democracy.

TODO/RFC:
 - discuss the WAGs for non-economic flags
 - how much weight should we put on the government goal in nation ruleset
 - remove government subgoal (pointless after this patch)
 - we need a "cooldown" period after having changed government once, where
   we don't want government techs at all for a while; otherwise we never
   get those ironclads
 - we should take into account how far up in the tech tree the government
   is and adjust accordingly; right now we sometimes want Democracy so
   much that Republic just becomes a roadkill
 - we ignore government tax rates (should perhaps call
   handle_player_government() instead of change government directly)
 - should be ready for general effects for governments

Please give some feedback.

  - Per

govai1.diff
Description: Text document