Use --relevel parameter for PCA plotting

[qbicStefanC]

Description of feature

The --relevel parameter in rnadeseq is primarily there for modeling in DE analysis ( i assume/recall). I just noticed that it has no influence on the ordering of the sample labels in the PCA plot. Expected behaviour would be that the releveling is also used for releveling of the factor levels in the PCA plot (although not that straightfoward because of the implemented combfactor , which is -in contrast- not used for DE analysis.

[qbicStefanC]

Leave this open until the next release.

Stefan.