OWSMath.swift overlaps somewhat with Math+OWS.swift but no worse than
OWSMath.h did previously. There are future refactoring efforts that
should occur there to use more of the extensions of Math+OWS.swift and
less of the extensions from OWSMath.swift
This included:
- Removing unavailable inits wholesale if no longer `required`
- Marking a few classes `final` so they could continue using
`Self(...)` rather than `OWSWhatever(...)`
