unified commands for Instrument drivers

While we integrate more and more drivers into qcodes we will have to make sure they can be used in a uniform fashion from the user perspective.
We might already run into this in @eendebakpt comment in #74
I guess all DMMs have basically the same main functions, but different special functions, the same goes for SourceMeters, magnets and others.
If we have single users working on a new driver we somehow cant force them to go through potentially tens of other drivers to figure out the optimum syntax.

How can we unify this?

Also in line with this, most instruments have a model name, a manufacturer, version, software version, i even think the visa *IDN? command is unified, at least it looks the same for the instruments I looked for.
In my drivers I did:

        vendor, model, serial, software = map(str.strip, self.IDN.split(','))

and put that data in a dict, however, I think this should be unified as well and be saved in the snapshot.
How should we go about it?

Start by reviewing the existing instrument drivers and the discussion in issue #74 to compare common DMM, SourceMeter, and magnet functions. Examine how IDN data such as vendor, model, serial, and software version is currently represented. Done requires an agreed uniform driver interface and a defined way to store instrument identity in snapshots.