update email handling

[bmartin5692]

598 was caused by unicode characters from the user's full name being included in the to header of the validation email.

I re-worked the email code to simplify and standardize it:

• Email header creation moved into EmailHelpers.py as create_email_headers

  • This sets the From,To headers properly encoding any unicode, which is what caused 598.

• Base64 encoding of the email body/template moved into EmailHelpers.py as get_emaiL_message

  • This standardizes the creation of an EmailMessage object, setting headers, and attempting the Base64 encoding, falling back to a normal email if it fails
  • As a bonus, this replaces the function I added previously 'email_rfc2822_compliance', as this solution encompasses that and is more robust

• Moved sending code into EmailHelpers.py as send_email_message

  • Changed from sendmail to send_message since we are using an EmailMessage object now

• Updated send_validate_message to use the new functions

• Updated create_validate_message to use the new functions

• Updated ForgotPasswordHandler to use the new functions

• Updated create_reset_message to use the new functions

[eljeffeg]

Nice Thanks!