A choice of 50 graphical player avatars and other quality of life improvements

Changes this week include:

* Implemented spell macros. Made a menu accessible through F2 which lists spells and allows the player to press a number and assign a spell accordingly. Made it so these are saved and loaded with the rest of save game data so that can be kept throughout the whole game. 

* Changed 'F' and 'M' so that it checks for last target and if none, then closest hostile. Streamlines ranged and magic gameplay a lot!

* Made it so that only the player and allies can be knocked out. It was just annoying as it was without any benefit - there were no circumstances where you would realistically want to heal or revive a neutral or hostile and monsters would rarely be in a position to do it either.

* Fixed bug where equipping enchanted ammunition gave bonuses to melee combat. Made it so that quiver slot is the one exception for added enchantment bonuses for equipment.

* Fixed bug where function which returned whether an actor could see another actor through darkvision didn't take into account the effect of distance. It's now properly restricted to 4 squares.

* Fixed bug where a monster might see an enemy and could still do ranged attacks or magic attacks despite that enemy moving out of sight.

* Began work on custom avatar for players. Implemented basic menu for selecting player avatars and allocated the standard ones for premade character templates. Added 50 avatars and completed menu for selecting and added F3 as key binding for this in-game so player has complete control at all times to change.

* Changed avatar selector to a red box to make things clearer after user feedback.

* Allowed NPC's swap places with an unconscious ally (including the player) to continue fighting rather than waiting for their ally to die first in close quarters combat. This required fixing a host of small bugs in my ai code which weren't noticeable until now, shifting the has_swapped flag from the ai component to the main object component to recognise the fact that the player object doesn't have an ai and allowing for an exception for swapping places when the player is involved - the player must be incapacitated to be swapped. If that exception wasn't in place, then NPC's would swap with the player all the time which was annoying but now they'll only do it and override the player if the player goes down.

* Fixed bug in companion ai where a null value was passed after conversion when it shouldn't have been.