[FEATURE]: StimEditGUI: support for dataLabels and condition names

[sstucker]

Currently, the tools for renaming conditions, adding conditions, deleting conditions do not work well.

No support exists for adding, deleting, or editing stim/dataLabels entries.

This is unrelated to BIDS implementation of "Event markers"-- it may be worth it to consider a StimEditGUI 2.0 milestone