RUVSeq to be optional

[lpantano]

Some downstream chunks rely on objects created during RUVseq chunk. To make this more flexible/plug-and-play with chunks people can remove, and since RUVseq probably wouldn't be used in a standard analysis, I would replace object names with more generic ones; in the RUVseq chunk you can just set those results to the more generically named objects if people want to include that particular chunk