Provide helper for parser about telnetpp

[KazDragon]

After some thought, it's probably not for the best that the interface is being weighed down so. It's getting little cumbersome. So it may be better to revert generate to trafficking only in vectors, and to introduce a "telnetpp::session" object, which can encapsulate all of the routing, parsing and generating behind three functions: install(option), receive(vector) ->vector and send(vector) -> vector.

Except even that looks a little lopsided with tokens on one side and elements on the other. Problem is that receiving data returns an immediate response that should be sent to the lower layer. The same isn't true of generating bytes for the lower layer with send.

[KazDragon]

I don't think I'll be able to get perfect symmetry out of this.