Make changes to unit script and add unit Factory to more easily creat…

[jomibauer]

…e units

• create GenericUnit prefab that only requires a name to have all its relevant sprites, stats, and items populated
• alter how Weapons, Inventories and stats are initialized so that each unit doesnt require such a in depth setup of its own prefab
• fix bug in UnitParser so stats dont get reset to zero whenever starting or stopping a scene.