@todo 1.9 rework that via extended event system
@todo 1.9: see_all -> false
@todo 1.9 add 'new units spotted' failure mode
@todo 1.9 set to false after implementing interrupt awareness
@todo 1.7.11 important! Add an ai action (and fai function) to set a goto on a unit
@todo 1.7.11 important! Add an ai action (and fai function) to send a chat message to a player
@todo 1.9 : consider allowing other engines to evaluate
@todo 1.9 replace with event system
@todo 1.9 add minor_gamestate_change_observer
@todo 1.9 optimize in case of an aspect which returns variant
@todo 1.9: add validators, such as minmax filters to aspects
@todo 1.9: replace with variant::null_variant;
@todo 1.9: check for (level_["disallow_recall"]))
@todo 1.9 add combatant.prob_killed
@todo 1.9: attack_prediction.cpp should understand advancement
		 * directly.  For each level of attacker def gets 1 xp or
		 * kill_experience.
@todo 1.9: lower this value for perf,
// but best_rating is too big for scout and support
// which give a too small locStopValue
// so keep costy A* for the moment.
@todo 1.7 check if this an improvement
@todo 1.7: ai goals: this is a 'target' marker class which should be expanded with additional information which is generic enough to apply to all targets.
@todo 1.9 refactor this
@todo 1.9 add formula_debugger
@todo 1.7: implement fai_ca->to_config()
@todo 1.7: serialize to config
@todo 1.9 rework that via extended event system, or at least ensure it hurts no one
@todo 1.9 extract to separate class which will use fai or lua parser
@todo 1.9 add error reporting
@todo 1.9 rework via extended event system
@todo 1.9 Refactor history handling and internal commands.
@todo 1.9 AI Interface command to clear the history.
@todo 1.9 move it out of public view
@todo 1.9 rewrite this function to use a fai or lua parser.
@todo 1.9: add information about ai_config