Bug 1016503 - [email] move sound preference into app, allowing email to be a privileged app
Merge pull request #308 from jrburke/bug1016503-email-privileged

Bug 1016503 - [email] move sound preference into app, allowing email to be privileged r=asuth
Bug 921050 - Send email in the background.
checkpoint
typos and nits
Update getMessagesBeforeMessage to treat date/id as a point, rather than a message that must exist.
Add GELAM tests for outbox cases as requested by @asutherland.