Add command to control local/remote/serial ionpump modes

It turns out that there is a semi-documented (not in table, but in narrative text) register for bth reading and writing whether the 4UHV ionpump controller. Register 8, 0/1/2 for serial/remote/local. We want serial for operations. And yes, you can remotely change from local to serial. Which may be why they do not document it well....