Release branch for 6.1.0

[jthrilly]

Network Canvas Server 6.1.0

This is the first significant feature update to Server since our launch. It implements an 'entity resolution' feature that allows a researcher to merge alters across interviews. Review the changelog below, and take extra care when updating if you are currently in the process of collecting data.

Changelog:

• Implements 'entity resolution'. This feature allows a researcher to 'resolve' nodes across different interviews, based on any criteria or methodology they wish. Consult the entity-resolution-sample repository for further details and documentation on using this feature.

[rebeccamadsen]

• [x] columns in Manage Cases view not sorting
• [x] spacing on the "x" for sessions in the Most Recent Sessions widget too tight
• [x] server advertising popup hides behind widgets
• [x] missing spaces around some bolded words
• [x] cannot copy the pairing code

[rebeccamadsen]

For the popup hiding, I tried changing the zIndex prop for the ReactTooltip in NetworkStatus, but that doesn't seem to help. We could make it go to the left, but I'm not sure if that will end up getting cut off vertically?