Read/create submissions from web form

[childss]

There should be an option to read incoming emails from an inbox and automatically create submissions from them.

• If email has attachment, treat as submission:
  • Read email address and name from the from field.
  • Parse email body as the email_text field.
  • Read attachment as the zipfile (and upload).
• If email does not have any attachments, mark as ignored or maybe flag for review by a human.

For the first pass, also mark emails with multiple attachments as needing a human. With #8 we could just make them all attachments to the submission model.

[AlabamaMike]

We decided to go away from using email as a submission channel in favor of a web form. The card title has been updated to reflect this decision.