Driver/keithley2600 fast sweep (#747)

* Add voltage range validation

With no explicit voltage range validation, the instrument will
silently do something not expected by the user.

Breaking change: the keithley must now be initialised with a model name.

* Add hardcoded current ranges

Nice to have.

Breaking changes: voltage ranges and current ranges now have new
parameter names.

* add display control settings

* update display_normal function

* correct normal display function

* Add ArrayParameter to hold the sweep

* Add scriptwrapper helper function

* squash! Add scriptwrapper helper function

* Add fast sweep function to instrument channel

* Add the sweep parameter and a user-level method to use it

* fix small things, add imports

* Fix: don't update the sweep parameter upon reset

* Add benchmarking notebook

* remote file that somehow snuck into this PR

* Add deprecation warning to un-channelised driver

* fix: internalise the model query

* fix snapshot and a misleading docstring

* docs: Provide new driver example

* delete old just-a-sketch driver example

* replace corrupt notebook

* delete unused import