Warn if number of physical samples doesn't match number of samples with metadata

Per Gail: Sometimes someone sends in metadata for a certain number of samples but the lab doesn't get all of them--e.g., metadata says there are 20 samples, but the lab only gets 17. The lab would like to be warned of this before they start plating those samples because they would like to wait until they get all the samples and run them all at once.

Note, however, that sometimes it *is* expected to get metadata for more samples than are plated, as in the case where some of the samples are for metabolomics, so either this would need to be a rather smart warning or it would need to be easily overridable.