Add ability to mark other phone numbers as primary
Refactor change default phone number button

Make default and delete post requests now submit the phone number as
part of the form instead of in the url.

The model method to set default phone number will now add a phone number
if called on something that doesn't already exist.
Remove unneeded url encoding of phone numbers
Fix broken phone user tests
Merge pull request #260 from dimagi/default_number

Add ability to mark other phone numbers as primary