Add multi-sample summary table to top of QC report

[lkwhite]

The current QC report is great for tracing individual samples' data but it could use an at-a-glance view of number of mapped + classified reads for each sample in a multisample run (plus perhaps a few key metrics).

Also, "Per-Sample QC Overview" plots of tRNA abundance and charging appear to show a subset of all tRNAs (31 species), but this isn't clearly explained anywhere. Are they the most abundant/charged 31?