Fix various bugs in Export: Merge Contacts with Same Address feature

Linked to NYSS issue: http://senatedev.senate.state.ny.us/issues/show/3698
Please track all hours and record there.

Expected Behavior for this Feature
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Merge Contacts with the Same Address will combine any records having the same address (street address, city, postal code, country) into a single record. If a household record already exists in which multiple individuals share an address, the household will be exported as the combined record. If no household record exists, the records will be combined and the Addressee field will list the contact names, comma-separated.

Bugs to be fixed
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1. Three individuals, same address, no address sharing (no household record):

• • correctly collapsed into a single export row
  • Addressee was a constructed concatenation of all three names (correct)
  • Postal Greeting (using default "Dear {contact.last_name}

    ) was not exported correctly. Exported columns contained "Dear Lastname (where one of the three Individual's last name was used). It should be "Dear Lastname1, Lastname2, Lastname3".

2. Shared address merge on export does not merge Individual contacts into Household as spec'd

• create Household A, Individual B (shares address w/ Household A), Individual C (also shares address w/ Household A)
• you now have two indivs sharing one household record's address
• select all 3 for export and check the "merge shared address" option only
  Should export ONLY the household record. Instead it exports the household + one merged row for the two individuals (with incorrect Postal Greeting as noted above).