3.0 - Optimize Inflector.

Use a single list of uninflected rules.

`$_plurals['uninflected']` and `$_singular['uniflected']` are almost identical and they are merged with `$_uninflected` when inflecting. So it makes much more sense to just keep a singe list. I also removed all proper nouns from `$_uninflected` and other words which would almost never be needed.

I also want to unify `$_plural['irregular']` and `$_singular['irregular']` into `$_irregular`. They too are merged when inflection anyway.
This will need to be added to the migration guide.