Update fgsLabels

[mlhale7]

Is your feature request related to a problem? Please describe.
This application doesn't currently allow users to update the Fedora Gsearch label. While the mods:titleInfo/mods:title is typically used for this label, there are a number of situations where we'd want to change the field used for the label across an entire collection. Serials/athletic programs are a good example of this. The title transcribed from the source(which goes in mods:titleInfo/mods:title) often has variations across the collection that make it not the best field to show for display purposes. Often a supplied title is created that makes it easier for viewers to browse results. It is important not to attempt to make MODS deal simultaneously with display issues and descriptive cataloging rules as the two here conflict (aka, if you try to dump a transcribed title in mods:titleInfo/mods:title[supplied] or [alternative] to deal with the display issue your MODS records are not representing the objects accurately).

Describe the solution you'd like
I'd like to see a solution similar to the one used https://github.com/markpbaggett/whitebread. This allows the user to define which MODS field should be used for the fgsLabel and changes it in a batch.

Describe alternatives you've considered
I have not seriously considered other alternatives.

Additional context
Consider this work knowing that we will be moving to a new platform in the future that may not have the same concept of a fgsLabel.

[markpbaggett]

@mathewjordan, do one of you all want to take this?