made viewport require parameters to be constructed.  type should be immutable.
added additional test for NYSE at Wall St.
added Equals for AddressComponent and LatLng to support NUnit but NUnit.Is.EquivalentTo doesnt seem to call it.
tried adding a few things for testing:
- (collection) IsEquivalent but nunit is ignoring AddressComponent.Equals
- a tolerance factor for comparing the lat/long values