Added history for email and username changes to userprofile model
Merge pull request #5326 from edx/will/profile-account-user-meta-field

Added history for email and username changes to userprofile model
Translate unexpected errors into API-specific internal errors
Merge pull request #5329 from edx/will/handle-db-errors

Translate unexpected errors into API-specific internal errors
Merge pull request #5334 from edx/renzo/change-email

WIP: change email
Remove unused import in tests
Require login and exact HTTP methods
Merge pull request #5339 from edx/will/require-login-for-account-and-profile

Require login and exact HTTP methods
New, more standard email templates
Confirm and complete email change requests, add tests