Implement power/slot limits and bonuses for those limits

The system for limiting powers and slots in Tempest is complex and will need some design work to get right. Initial thoughts:

The absolute limiter is the "Active Powers / Prepared Spells" pool (and a similar Cantrips/Utilities pool), which is determined by character level. Regardless of what power or spell slots appear in your class table, you can't have more martial powers purchased or spells prepared than this number.
Except that you can get bonuses that apply only to Active Powers or Prepared Spells from various sources, so the single pool is more of a Venn diagram.
Extensive Combat Training grants the ability to choose an additional power from a martial class, but doesn't grant an additional active power slot. This is likely to allow a multiclass character with active power slots to burn the ability to gain a new power from one of their classes despite already being at that power tier's limit for the class... but we should verify the intent.
Multiclassing also makes this weirder, because you get a bonus active power/prepared spell/cantrip/utility power for the first level of any secondary class you take, and your slots/tiers/whatever work as though you were twice your level, but only up to the primary class's tier? There's a lot going on there.

kw / camp