Corrected syntax to use the perl defined-OR operator
Define-OR (//) was used originally because the boolean can return true or false
and we want to know when it is undefined (because the database entry is
NULL). This was corrected in error in a prior commit. This commit
essentially reverts that change.
retrieve_gene now calls find_gene to get the gene symbol from the local
Solr index
Modified Gene plugin to return expected keys for retrieve_gene and
updated tests
v0.253

    Replaced retrieve_gene with find_gene to correct missing gene symbols throughout LIMS2