Squashed commit of the following:

Author: Christopher Tate <ctate@google.com>
Date:   Mon May 4 16:38:11 2009 -0700

    IBackupService now passes ParcelFileDescriptors rather than int fds

    The outlines of backup state file / data file handling are now in place as well
    in the BackupManagerService.

Author: Christopher Tate <ctate@google.com>
Date:   Thu Apr 30 12:40:19 2009 -0700

    Hide the backup stuff for now

    Also adjust based on comments:
    + changed service intent string to conform to usage guidelines
    + only publish the IBackupService binder when invoked with the right
      intent action
    + docs tweaks