Support simultaneous processing of multiple spectra and/or compounds

[alexeigurevich]

Currently, NPvis is designed for handling a single compound-spectrum match. However, the NPvis use case scenarios might include

1. Evaluating multiple candidate annotations for an MS/MS spectrum
2. Selecting the best spectrum per compound among several tentative identifications

Now, this could be done via multiple runs of NPvis but we should think of a more user-friendly implementation.