Add parsing for software-information query type.
The code already supported sending software-information queries, it
just didn't parse the reply correctly. So, TransportContentParser
now knows how to deal with software-information replies.

These software-information queries aren't in the netfconf RFC, but
are in the Junos 1.0 capabilities and are the typical way to get
the hardware and software version information from an JUNOS device.
Merge branch 'parse-software-info'