"generic" host interface

quite often users want to have a host that they are checking with simple checks - tcp ports, icmp ping (or maybe external check scripts).

for these hosts, they might not run agent, snmp, jmx or ipmi, thus none of the existing interface types matches.

it might be useful to introduce "generic" interface type.

note that this only aims to improve usability and reduce confusion - functionally, there would be no gain, as one can assign these items to any interface type already.