Bring back "infer" functionality

[jrlegrand]

Infer functionality was really built as part of the API and lost as a core part of the script. It would let you include an NDC or RXCUI with the free-text sig and it would fill in the blank using RxNorm where possible (i.e. if the NDC was an oral tablet, and the sig didn't specify a dose unit, it would infer a dose unit of "tablet").

This will require updating the optional arguments (as well as the CSV input file) to accommodate NDCs and/or RXCUIs in addition to sig text.

This is the infer method:

parserx/parsers/sig.py

Line 154 in b747c1f

def infer(self, match_dict, ndc=None, rxcui=None):