Here is an aggressive PoC rewrite to simplify the library,
while retaining most of the functionality.

Some specific points:

- Remove the special `MasterStatus` class.  This design was awkward,
  because it was a subclass of Status, but provided functionality
  that should have been provided by the StatusPool,
  resulting in a lot of edge case code.
  - Merge required functionality into the StatusPool.
- Remove unnecessary classes; the clobberer classes could be pure functions.
- Rename clobberer to summarizer
- Leverage more existing code:
  - use UnknownStatus as-is
  - use StatusBase.from_name
- Remove some magic, but retain just enough
  to still support `pool.status_name` get/set access shortcuts.
- Remove the static subclass based approach to defining the pool
  (it's cool, but feels too magical, and I think in practice
  the procedural method of building the pool will be more practical).
- Consolidate status tag and attr into a single name.
- Remove the externally managed private variables from Status class.
- Remove static class variables from Status class (originally for tracking ids for ordering)