Adding e4crypt support

Add file encryption flag to fstab.

If file encryption flag set in fstab, handle identically to block
encrypted volumes.

Requires matching change:
  https://googleplex-android-review.git.corp.google.com/#/c/642778/

Change-Id: I28c236959f2d7d5f0dccc8ea45c325ea0cf871fc
9 files changed