Bug 1033475 - Allow user to configure email preferences from their profile

Update User Profile edit screen to allow email preference
Update text on account creation screen to indicate how to remove consent to email
Don't send email address in feedback email if they have not consented
Hide user email from most admin screens if they have not consented to receive email
Add consent_to_email field to UserProfile
Change OneAndDoneUserManager.get_query_set() to from select_related to prefetch_related due to https://code.djangoproject.com/ticket/15040

Should secure Auth - User admin to superusers only so that not everyone can see all the email addresses
nit: please wrap lines to 100 chars. Makes the code easier to read and review and it doesn't affect translations.