[SCHEMA] save UserInfo about Google OAuth Account (name, locale, etc.)

Test Plan: run the migration and re-auth

Reviewers: spang

Differential Revision: https://review.inboxapp.com/D81
Replace polling with IDLE

Summary:
    This commit replaces polling on the Inbox folder with the IMAP IDLE command.

    FUTURE TODO:
    * Make sure server supports IDLE via CAPABILITIES command. For example, Yahoo doesn't.
    * Utilize returned Sequence IDs to quickly fetch new messages (though likely won't do this)
    * Make `IDLE_FOLDERS` dynamically configurable via API
    * Consider not doing a HIGHESTMODSEQ and instead just fetch all UIDs when IDLE returns, since it only

Test Plan: Add/remove mail from the Inbox folder, which should trigger an immediate IDLE callback

Reviewers: spang

Reviewed By: spang

Differential Revision: https://review.inboxapp.com/D80