Simplify `plotPCA()` method support for bcbioRNASeq, and add support for `title` argument. Deprecated `returnData` in favor of `return` argument.
Simplify `plotPCA()` method support for bcbioRNASeq, and add support for `title` argument. Deprecated `returnData` in favor of `return` argument.

hbc/bcbioRnaseq,roryk/bcbioRnaseq,hbc/bcbioRnaseq