Special navigator for numbers to work on maps, lists, or vectors

[nathanmarz]

For the implicit nav for numbers, should consider making a non-public navigator that will work on maps, lists, or vectors (currently uses keypath which works on just maps and vectors). This navigator would have to do an instance check on the collection type to determine how to access it.

[nathanmarz]

Decided against this as it's better to keep the implicit behavior as simple as possible.