RNA-seq ERCC QC

Perform QC of the ERCC spike-in for models aligned to the ERCC spike-in FASTA and annotation (in addition to the reference genome/annotation).

The hashref is `$ercc_hash_ref`, so these would either need to be `$ercc_hash_ref->{...}` or `$ercc_data{...}`.  (Probably the latter if we're going to the trouble of having both.)