SPARQL and iTQL

Going forward we would like all new triple store queries to use SPARQL when possible as iTQL is implementation specific. When iTQL is deemed necessary for supporting older implementations we can use the new method for offering two queries as exemplified in https://jira.duraspace.org/browse/ISLANDORA-1459 . The technique involves checking the new Drupal variable islandora_risearch_use_itql_when_necessary to decide which language to use as shown in https://github.com/Islandora/islandora_oai/pull/75/files . The goal is to allow for the swapping out of the default triple store for a different implementation.