SPARQL: check syntax for triplestore swap

[jefferya]

To test:

• Voyant connector - pass in a collection PID

https://github.com/cwrc/islandora_plotit/blob/6e9e4ff9196e7c418ebdf28997c72c368e111a3d/includes/voyant_helpers.inc#L29-L38

[jefferya]

ToDo:

• add: PREFIX fedora-rels-ext: <info:fedora/fedora-system:def/relations-external#>
• remove angle brackets: fedora-rels-ext:isMemberOfCollection