This updates the @spina decorator to support the kinds of options

available to base classes. Subclasses can now set names and apply

mixins.
A new _prepareSubclass handles the common functionality for the

mixins, and will soon handle new options as well for both base classes

and subclasses.
To support passing in options to the decrator, the bulk of the logic

from spinaSubclass has been moved into an internal

_makeSpinaSubclass function. The existing spinaSubclass now chooses

how to call that and what to return based on whether or not options are

provided. If options are provided, a function is returned that itself

take in the decorated class. This works much like how Python decorators

do.
We declare types for both variations of the decorator.

Tested this (along with upcoming changes) in Review Board, ensuring all

tests run.