Prepare for separate Exchange application

* Remove reference to certificate in (the certs will
  be derived from the directory, i.e. Exchange vs ExchangeGoogle)
* Remove sharedUserId and process name from manifest
* Change loadAttachment to use AttachmentProvider to open attachment
  files for writing
* Always retrieve deviceId from Email app

Bug: 3442973
Change-Id: I70ddb4d2971e481b0d4def09944e54d23ef431ec
5 files changed