Add missing "Notify for every message"...

Since Email now uses UnifiedEmail, this setting defaults to false
and there is no way to enable it; this commit adds this option,
which is then honored by the unified notification engine.

Change-Id: I5d4464026c6532c9aac87016368cf8e13d9cfbb5
Email: Add new check frequency options (2h, 4h & 1 day)

- Ported from cm-9 & cm-10

Change-Id: Ia59f4e8db5e7458a0e12d5530c25589cc84a79bf