Input checking code for QuickOmics_DEG to be put into EArun to execute at start

[ferg-0]

Checks on the model rank, empty subsets, only one level within subsets. Keep as separate function to be called at start of EArun execution. Separate function for DESeq2 and limma.

[z5ouyang]

To @ferg-0,
This is updated by @wli7 with 06303f8
and incorporated with 25e3315.