Bug 821683/Bug 820317 - [Email] Confirmation overlay didn't sync with building-block. r=asuth. (cherry picked from commit fd1dce6e1b56a21a11b7c801408ecb57da1591b3) a=approval-gaia-v1 on bug 821683.

Conflict was from https://bugzilla.mozilla.org/show_bug.cgi?id=811858 not being
present on v1-train.

Conflicts:
	apps/email/js/compose-cards.js
Merge pull request #8077 from asutherland/email-confirm-dialog-v1

Bug 821683/Bug 820317 - [Email] Confirmation overlay didn't sync with building-block. r=asuth. (cherry picked from commit fd1dce6e1b56a21a11b7c801408ecb57da1591b3) a=approval-gaia-v1 on bug 821683.