New plot tool: subsampled gene counts

Added a new tool - take a group of BAM files (typically RNA-Seq), subsample them, run cufflinks on all of the subsampled files and plot the number of genes observed versus the subsampled read counts.

Designed to give a more intuitive / biological angle on the preseq complexity plot.
Yeah I know, I wrote in the readme that these file would need to be updated ;) To be honest, these first steps are fairly manual at the moment so not production ready in larger ways than just hardcoded strings - several jobs failed when I ran these so I think they need to be run a few times to actually get all of the cufflinks jobs to run. Plus it takes ages. Finally, they should really be run by a pipeline manager to give dependencies to that the substeps don't have to be fired manually.

So yeah, I'll leave all of that until another time, if ever the plot is needed in a larger scale environment.