email: allow to remove an email account

Change-Id: Id9ae4f09487c918ebfae9d1854b675e52aee534f
JIRA: CYAN-3420
Issue: https://jira.cyanogenmod.org/browse/CYAN-3420
Signed-off-by: Jorge Ruesga <jorge@ruesga.com>
Merge "email: allow to remove an email account" into cm-11.0