Add EasService & PingSyncSynchronizer.

This is the first step to decoupling actual sync execution from
the mail sync adapter. This change does not yet move to using the
new service, it only adds the code and necessary changes to existing
operations to be compatible with it. This change should not affect
existing functionality.

Change-Id: I80663c2bc216fdee44756d83fd567bc2c447e993
(cherry picked from commit 6c715246946dc4a7b7ca535dd9ff7f3cfc227c6d)
12 files changed