notes for scRNA

* explain the protocol in the beginning
* barcode figure to the beginning
* separate slide deck
* figure how we put both fastqs together ...?
* amplification bias?
* understanding plates and batches ...
* figure instead of ascii art?
* put that into the slides
* put the numbers in the info field 4096, 1024 and so on ...
* do not call it MPI plate setup

ping @mtekman

Use this issue's scRNA notes as the starting point; clarify the protocol, barcode figure, separate slide deck, FASTQ combination, amplification bias, and plate/batch explanations. Done means the requested material is organized in the training content, figures and numeric details are included, and the MPI plate setup wording is replaced.

Written by the indexing model from the issue text.