NPCs!

Finally implements the missing NPC Actor type.
The sheet for this is significantly simpler, however.
It does not do automatic Artha tracking, and many of the custom calculations can be manually entered.

Sheet operates in 2 modes:

• Edit mode, where items can be deleted, skill exponents can be set, etc.
• Regular Mode, the typical compact mode of play, where rolls are made

This release also includes a minor usability improvements to the toggles on various item sheets, enabling the default keyboard navigation behaviour one would expect.