In addresses resource, add support for a locality proximity check

[mraross]

In the physical address intake forms of many client-facing applications, localityName is entered in a separate field. Such an application could include both addressString and localityName in geocoder requests to allow the geocoder to do a reasonable proximity test before accepting a given match. Here's a proposal:

In addresses resource, add support for a locality proximity check.

If a localityName parameter is provided in addition to addressString, the geocoder will reject any matches that are beyond a certain distance from the named locality.

We could also add support for a localityRange parameter that specifies what the threshold distance is with a default of 60 km, which is what MCFD is currently using.

[cmhodgson]

This overlaps with the streetAddress concept #63 as the street address is the rest of the address besides the locality. Additionally here we are saying that we treat the locality as a "fluffier" matchable locality, not a hard exact locality - this might use the distance based locality mappings concept from #357 .