Add support for `Exclude IDs` from test spreadsheet

[gaurav]

This is a pipe-delimited list of identifiers that should not be cliqued with the primary identifier.

[gaurav]

This could also be implemented with e.g. "^MONDO:1234" to mean that MONDO:1234 should not be returned in a particular way. If so, this could replace the "negative" flag in the "Flags" column.