Single-Sample SomaticValidation CoverageStatsSummary

Update the coverage stats report to allow for duplicate tumor/normal pairs.  Only uniquely report each sample/roi/processing profile combination once.  If multiple processing profiles are seen, fail.  Also allow for OPTIONAL normal_sample from SomaticValidation model types.
These messages might be easier to read if they take advantage of generic quoting and the fact that `status_message` &c. acts like `sprintf`, e.g.:
```perl
$self->status_message(q(Duplicate sample '%s' and region of interest '%s' allowed, but only reported once in output), $sample_name, $roi_name);
```