Bipolar electrode labeling

[adam2392]

Describe the problem

Each pair of contacts on each electrode (for SEEG) can also add a suite of bipolar contacts (e.g. the centroid location) and also their downstream anatomical labeling.

This would help provide anatomical reasoning of the bipolar reference analysis of iEEG data.

Describe your solution

Just compute mean of the localized contacts in 04-contact-localization and then apply them as an "electrode" in downstream labeling.

This should be there... by default? Then anything setting "montage" of electrode locations in programs only needs to set locations from rows that have the channel name correctly.

Additional context

cc @TheBrainChain