Migrate push to new architecture.

The most interesting part of this change is the new code
in EmailSyncAdapterService to handle sync issues between
pings and syncs. Most of the EasPingHandler is adapted from

The other big piece is the migration of the IEmailService
to the EmailSyncAdapterService.

After this change, there is still cleanup for error paths
and cauterizing the old ExchangeService to be done.

Change-Id: I3a5cca8bdc51dad80cb2e83e09562fec8d05d235
6 files changed