Modifications to allow NRPE arguments (dont_blame_nrpe) in the config-web

With this change we can allow pass arguments from Nagios server to pfsense, and
allow them or not from the NRPE config web. 

To get a config file with $ARG1$ $ARG2$... we must scape them in the
"Extra options" input and put \$ARG1\$ \$ARG2\$...