Enable running pipeline on a single lane of a sequencing run

[AmandaBirmingham]

We have had two instances in which one lane of a sequencing run had data ready at IGM but the other lane didn't, and therefore we had to wait for both to be ready before running the pipeline. This is because the pipeline requires that sequencing run names be unique; running data for the same sequencing run name twice (e.g., once for lane one and once for lane 2) would overwrite the lane one data.

The requirement for a unique sequencing run is baked pretty deeply into the code, and it would take meaningful effort to change it. However, if this is a situation we expect to encounter frequently, perhaps it is worth the work.