General protocol buffer approach

[KristianLyng]

With USP, we now have two protobuf family parsers. We should expect more.

A general-purpose protobuf parser would be nice. I envision the general logic as:

1. Do proto.Unmarshal() onto an interface{}, named Data
2. Do type casting on the Data, checking for known protobuf messages
3. Allocate a subtype struct depending on the type of Data, e.g. USP for USP, Junos for junos, call it PType
4. Issue PType.GetTimestamp, PType.GetMetadata and PType.GetData (or similar)
5. Do some sort of common normalization at the end, e.g.: PType.Nornalize()

This is obviously just marginally processed thoughts, and the algorithm could be widely different, but I think at least step 1-3 is probably sensible?

This would allow us to actually have a general-purpose protobuf parser.