Email split, part deux: PolicyService

* Split PolicySet from SecurityPolicy and move to emailcommon
* Define PolicyService that sync adapter services can use to
  interact with the Email DPM administrator
* Implement PolicyServiceProxy for exchange
* Implement PolicyService in email
* Modify imports, references, etc. as required

Bug: 3442973

Change-Id: I92015e21f780a68754b318da89fbb33570f334a2
5 files changed