crossover_wmd repeats a node identifier

[ajnelson-nist]

The UUID 99d72bac-8c21-11e9-8902-0c4de9c21b53 appears in a few IRIs across the data on the website (including in at least Crossover and Owl Trafficking), with each usage pertaining to a different node.

In the Crossover WMD example, it is recorded as a "sender" in this email message (link goes to today's state):

https://github.com/casework/casework.github.io/blob/eb6ce8a/examples/crossover_wmd/crossover_wmd.json#L271

Because there isn't currently a check for uniqueness per Facet type, it hasn't been caught that the node is repeated, and via Facets, ties to two different email addresses.

What should be the email address associated with the sender of kb:emailmessage-2c032220-8c21-11e9-9c99-0c4de9c21b53?

Note: This Issue does not necessarily imply that I agree with the use of the sender field in this example.