Made Firewall rules persistent

In order to support pre and post scripts that should be executed on all
configured servers, it was necessary to:
    * Rename global_000.py into prescript_000.py (since it already acted
      like a pre script)
    * Created postscript_949
    * Created (pre|post)script.pp

Change-Id: I766ad3a5fb7a4a2230d9fdf769dfcb85772485ac
Merge "Made Firewall rules persistent"