Instead of indexing `Key` objects that have multiple names by each
individual name, index by the set of names. This reduces the size of the
default key dictionary by a factor of between 2 and 3, and as result
also reduces reallocations/defragmentation.
Instead of instantiating all module/extension keys by default, append
them to the `maybe_key`-generator list.
Before, the allowed alphabet of characters for CapsWords was exclusive
of the letter Z, and the allowed number set was exclusive of the number
0.
Now, those characters are included, so using them won't interrupt
CapsWords.
