add RaspberryPi read-only guide
add RaspberryPi read-only guide

emoncms/emoncms,chaveiro/emoncms,chaveiro/emoncms,emoncms/emoncms,inverse/emoncms,inverse/emoncms,inverse/emoncms,jeremypoulter/emoncms,jesjimher/emoncms,jesjimher/emoncms,emoncms/emoncms,emoncms/emoncms,jesjimher/emoncms,jeremypoulter/emoncms,inverse/emoncms,jesjimher/emoncms,thaipowertech/emoncms,thaipowertech/emoncms,thaipowertech/emoncms,thaipowertech/emoncms,chaveiro/emoncms,chaveiro/emoncms,jeremypoulter/emoncms,emoncms/emoncms,jeremypoulter/emoncms