Email: Ensure that the service is not null before checking for sync

The google fix:
                // Fix up the Calendar and Contacts syncing. It used to be possible for IMAP and
                // POP accounts to get calendar and contacts syncing enabled.
                // See b/11818312

fixed up this case. But if the service (eg ExchangeService) is not available it breaks with a NullPointerException.

Just check against null to fix it.

Change-Id: Ib3fb2b9c0ba8df2062250b4143a54bd99e881bea
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
Email: Add native heads up support per account (1/2)

Add native heads up notification support. User can set on every account
if he or she want this account as heads up notification or not.

This patch adds the settings for it as well the complete handling. Due
of a half broken NotificationCompat.Builder class we switch here to the
Notification.Builder class to get access to the methods we need. This is no
problem here due that we do not need compatibility on lower API's

Adapted to LP

Change-Id: Ia88d2f15f0eaf7ae024ab07dd4f74c6858f17f76
Email: Update the widget preview image

Change-Id: I97fbbdbbc0223957eb2733a658454e94f46f9d42
DBHelper: Support upgrades from SlimKat

Add the new columns when coming from v126, add the old ones when
coming from any other value (or creating) so that they're there
when the feature gets reintroduced

Change-Id: I48ec042b30afbcefd43bdad0042147b6b0d2249f