add job options to workflow

Give each job finer control over how a job will be run and verified as
completed.

	modified:   modules/Accessory/lib/CoGe/Accessory/Workflow.pm
enforce gsnap job to have non-blank results

The pipeline will not continue if none of the reads map to the genome.

	modified:   scripts/qteller.pl
add read depth experiment to pipeline

Add steps to extract read depth information and create a new experiment.

	modified:   scripts/qteller.pl