convertToGeneAnswers should accept list names

`convertToGeneAnswers` constitutes a wrapper function for converting the results of the doEnrichment function to a GeneAnswers-class object.

To run this function, one must pass a data.frame containing the gene identifiers that were enriched on as the `geneInput` argument.

Given that enrichment can be run using either a list of ids or an InterMine list name, it would make sense if `convertToGeneAnswers` would accept a list name for `geneInput` as well - otherwise we have to run a query to fetch the list contents client side, even though we didn't need to do this for the enrichment in the previous step.