Account Data: Shared email model

[toddheasley]

Accounts operate on a standard, shared Email model. Email model features:

• Decode Email from IMAP.Message or JMAP.Email
• Encode Email to SMTP.Email or JMAP.Email
• Interface to view and compose new HTML Email
• View and set shared Flag model Account Data: Shared flag/label model #300

[thundernotion]

Issues with a parent cannot be on the Milestones board, removing. Either move your sub-issues up to the parent issue, or turn this into an independent Milestone issue that has sub-issues.