Transform into a complete CLI Mail App

[avikumar15]

Implement various other features of a typical mail app in the CLI

• User should be able to see a list of all labels and navigate to mails contained in them.
• On selecting a particular mail he should be able to see the content of the mail.
• Allow user to delete and trash some specific message
• Allow user to add/delete a mail to draft and retrieve all emails from the draft

Refer the doc