Version 2: Spellcasting

[ebshimizu]

bit of a tangle here

• clean up spells.json
• hook up editor fields for basic spellcasting stats
• move class-specific spellcasting fields inside the class spellcasting section
• class-specific spellcasting: spell slot entry and editing
• class-specific spellcasting: rendering (including custom preamble)
• innate spellcasting: list creation and editing
• innate spellcasting: rendering (including custom preamble)
• clean up: separate class and innate spellcasting to separate components

a button for custom spell creation will exist but actually making it do something is a different issue (#56 to be exact)