reposync: make less verbose

  Patch Set 2: Make a system settings so user can toggle.
    Add AOKP_REPOSYNC_QUIET=true to your .profile/.customrc
    to make less verbose, default repo behaviour by default.

Change-Id: Ief4a832aba118216b139d615f29d1b86f1717ba2
Merge remote-tracking branch 'aokp/kitkat' into kitkat