Small

1. Add Relationship between skills and skill categories
2. Remove Tables and replace with CSS Grid
3. Fix unaligned CSS
4. Prevent Duplication on Drag and Drop for Skills and Skill Categories, possibly spells too.
    DONE - Overriden _onDropItem on Player Sheet
    DONE - Skill Categories cannot be renamed if they are owned.

Medium 

4. Inventory sorted by types
    i. Drag and drop should add an item if it already exists.
    ii. Equipables
    iii. Favorites
5. Creature Sheet

Large

6. Dice Roller
7. Initiative System