(WIP) Start implementing ICombatant

Start by replacing `hitMob` with `takeDamage` interface function.
Simplify `pcAttackChars` a little by utilizing the new interface, then add more interface functions as needed.

A lot of the combat logic is tied to the `Mob` class. Need to start moving stuff over to CombatNPC.

src/Combat.hpp

@@ -23,6 +23,5 @@ namespace Combat {
     void init();
 
     void npcAttackPc(Mob *mob, time_t currTime);
-    int hitMob(CNSocket *sock, Mob *mob, int damage);
     void killMob(CNSocket *sock, Mob *mob);
 }