Features/162 geosubmit

This adds a new geosubmit API to close out #162
We should adjust the fallback value to be -1 for both home* values. Here and in the geolocate schema. We use -1 for mcc/mnc defaults everywhere else. Since we don't actually store these fields, changing the default shouldn't change anything else.

And I'd indeed not store these values, just accept and ignore them. I don't think knowing that someone is an AT&T customer but currently roaming adds any value for us.