Processor for Agilent 2-color data

For Agilent two color experiments that have raw data available, we can use [`SCAN.UPC::SCAN_TwoColor`](https://bioconductor.org/packages/release/bioc/manuals/SCAN.UPC/man/SCAN.UPC.pdf#Rfn.SCAN.Rul.TwoColor.1) for processing. This gives us the output of the two channels separately.

Would be great to run a handful of experiments through a processor with `SCAN_TwoColor` in development and gain some insight into the following:
* Are paired channels highly correlated (within a sample)? [Reported](https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2375008/) to be of particular concern in probes with high GC content
* Does there appear to be strong dye bias (i.e., do the two channels cluster apart from one another)? (This "dye bias" could be driven by the use of a common reference like [Universal Human Reference](https://www.genomics.agilent.com/en/References-Controls/Universal-Reference-RNAs/?cid=AG-PT-172&tabId=AG-PR-1217).) Could any dye bias be mitigated by quantile normalizing (using Affymetrix reference) the channels separately?

Looking a bit into the future -- could be useful to _automatically_ detect control/reference channel.

cc @srp33

No repository file or test is named; start at SCAN.UPC::SCAN_TwoColor and run it on a handful of Agilent two-color experiments with raw data. Compare paired-channel correlation, dye bias, and separately quantile-normalized channels, then document the findings and whether automatic control/reference-channel detection warrants follow-up.

Written by the indexing model from the issue text.