fixes #470 - Add gpxe scripts support

• dynamic gpxe script that kickstart purly with gpxe - see usage example below
• add static network option to kickstart, ie if added ?static=true to the url, network configuration would be static
  at the moment this should only be used with gpxe, or alternatviily you would need to
  provide the network information as a kernel argument (see gpxe_kickstart_config file as an example for that.

gpxe usage example

press ctrl-b for interactive mode
#get network from dhcp
dhcp net0
#or set static
ifopen
set net0/ip <your host ip>
set net0/netmask <netmask>
set net0/gateway <your gateway>
set net0/dns <dns server>

1. tell gpxe to ask foreman for instructions
   kernel http://foreman/unattended/gpxe_kickstart_config
   boot