Also added functionality so that runWorker can be run without
specification of an analysis.  The create_new_worker method now will
query for a 'needed worker' analysis from the AnalysisStats adaptor when
the analysis_id is undef.  This simplifies the API interface between the
Queen and the beekeepers.  Now the beekeeper only needs to receive a count
of workers.  The workers can still be run with explicit analyses for
testing or situations where one wants to manually control the processing.
Now one can simply do
bsub -JW[1-100] runWorker -url mysql://ensadmin:<pass>@ecs2:3361/compara_hive_jess_23
to create 100 workers which will become whatever analysis that needs to be done.