feature/health_config

There were quite a few settings for establishing the policy for health (non)computation, so I broke them out into a submenu and separated the 'vanilla' settings from the variant settings. The variants tab only has a couple of settings right now, but I intend to add a few more soon.

Also expanded the fidelity of control of hitpoint computation by separating what was previously tied together. Numeric rates and number of maximized die can now be specified numerically. The rounding style and when to apply rounding has also been exposed to the user. Some of this could be interpreted as a bit complicated, so I provided the settings for PFS legal play as a hint.