CLC-3174: FinAid Messages: diagnostic message has a URL that we don't show... should we?

https://jira.media.berkeley.edu/jira/browse/CLC-3174

For diagnostic messages, stop looking at the <URL> attritube and pay attention
only to "Supplemental Usage Content[Type='URL']"
Merge pull request #2095 from chikoon/CLC-3174-myfinaid-unshown-diagnostic-message

CLC-3174: FinAid Messages: diagnostic message has a URL that we don't show... should we?