Add support for single-shank Neuropixels 2.0 probes

[bparks13]

This PR is now targeting #523 as its base branch; the refactor of the Neuropixels V2 classes are now in that branch, and all single-shank specific changes are enclosed here.

• Update shift register bit setting for single-shank probes
• Add combo box to the 2.0 GUIs allowing the user to change the probe type
• Instead of reverting to the default settings for a probe type if the user switches types, hold both configurations in memory and swap between them so that the user does not lose any configurations accidentally

Fixes #446

View of the editor:

The properties will not appear different to the user, but on the backend the type has changed. This does not affect old versions being loaded, as the type is not recorded in the XML file, only the name and the properties.

Example GIF: Changing Probe Type Manually

In the above GIF, we can see how the user will interact with changing the probe type, and how it affects the drop-down menus for the reference and electrode presets.

Example GIF: Loading Saved Files and Loading Default Configuration

This example shows how the user can load a saved file (either single- or quad-shank); it gives a warning if the current probe type does not match the incoming type, but does allow the user to continue if they wish. If the types match then no warning is given.

The default configuration is based on the selected probe type.

Testing Required

I do not have access to a single-shank Neuropixels 2.0 probe, so this will need to be tested with one of those probes before we can merge this PR.