Changed interface of IPrerequisiteTrigger, ISetupTrigger, IPrologTrigger and IEpilogTrigger.
Major refactoring on command system:
* Setup trigger is now removed;
* Common usages of setup trigger is classified into 3 "conditions":
* * Mana;
* * All remaining mana (and old implementation is incorrect);
* * Spell target;
* These three conditions now can be registered in Prerequisite trigger.