New version release - list of changes, new features and bug fixes

This week saw me do a bit of the background work needed for more items. Each weapon and armour type got its own unique tile along with a few other changes and bug-fixes. Items are still a work in progress and I hope to get a fair few more done in the next week along with magic weapons and armour. The systems for magic items is already builty but I've got a few issues to work out in terms of displaying them when compared to normal items. 

* Added unique tiles for each armour and weapon type along with other miscellaneous items.

* Changed number of wizard starting spells to 3 level 1 spells along with 3 cantrips. Changed number of new wizard spells per level up to 1 per level.

* Fixed bug with magic missiles causing doubling up of targets because of AI being able to use the spell.

* Properly implemented benefit of constitution bonus for level up. Previously didn't recalculate this for all pre-existing character levels. Fixed this by tracking the unmodified base max HP from character creation and recalculating this from scratch on each level up by adding the HP bonus per level arising from constitution (and dwarvern toughness).

* Implemented potions of healing. Added custom graphical tile. Fixed some old bugs to do with items which can't be used as equipment which have lingered because this is the first non-equipment item to be implemented. 

* Implemented vial of acid. Thrown one-use projectile which causes 2d6 damage.