Local hub prefix discovery

Some applications need to discover the prefix(es) under which they can publish data / which Interests the local hub will be able to forward down to the application. In order to discover that, applications need to send an Interest for /localhop/nfd/rib/routable-prefixes prefix. Response data to the Interest contains a list of prefixes and should be encoded as follows:

Response ::= DATA-TYPE TLV-LENGTH
               Name (= /localhop/nfd/rib/routable-prefixes/[version]/[segment])
               MetaInfo (= ResponseMetaInfo)
               Content (= ResponseContent)
               Signature

ResponseMetaInfo ::= META-INFO-TYPE TLV-LENGTH
                       ContentType (= BLOB)
                       FreshnessPeriod (= 5000)

ResponseContent ::= Name+

Note

ResponseContent should contain at least one Name, which should be routable towards the face from which the request has been received. The requester may process the list of returned names and pick whichever it wants to use.

For now, the /localhop/nfd/rib/routable-prefixes data is served by ndn-autoconfig-server.