mapper stream to separate concatenated unit numbers

[missinglink]

note: branched from #500

as noted in #499 some sources have the unit and housenumber concatenated.

this PR solves the issue for the most common cases in AU/NZ and opens up the possibility for expansion in other countries.

closes #499

[missinglink]

this PR will be particularly helpful in Australia, currently we're seeing results like this:
https://pelias.github.io/compare/#/v1/search?text=10+brunswick+st%2C+fitzroy&debug=1

[missinglink]

This looks good-to-go, the results for /v1/search are markedly improved:

Additionally the GNAF mapper is still working as expected:

Worth noting that the results for /v1/autocomplete are still not great:

This is mainly due to a decision I made to not modify the name.default (which is trivial to do).
The tradeoff here is that we would get similar results to /v1/search at the cost of the unit number not being included in the label, and therefore making visual deduplication more difficult.

I suggest we merge this as it's only positive and discuss a new ticket where we modify the name.default for these AU/NZ records in such a way that it doesn't include the unit designation, we can then modify the label generator to prepend in the unit number to the label in a locale-aware way.

[missinglink]

acceptance tests looking 👍, merging this.