[Feature Request] Rework ModificationInfo's implementation of IBioItem

[kMutagene]

Is your feature request related to a problem? Please describe.
IBioItem fields Symbol and Formula implementations in ModificationInfo are either placeholders or incorrect in some cases

Describe the solution you'd like
Symbol creation following some kind of convention (also helpful for prettyPrinting) and a more clever way of representing formulas than applying the modification to an empty formula (what happens on 'loss' modifications? Isotopic modifications?)