Changes roundstart AI law behavior.

There is a new compile option, DEFAULT_LAWS.
If set to 0, roundstart AIs will just start with asimov.
If set to 1, roundstart AIs will start with the lawset defined in config/silicon_laws.txt.
If set to 2, roundstart AIs will randomly choose between Asimov, Corporate and Paladin as their starting lawset.

The default is 1, and the Asimov lawset is in silicon_laws.txt by default.

Also fixes some posssible thing that could be a bug maybe in the ai's announce-laws thing. Reaaaallly minor.