Add free text signature parsing

[brynrhodes]

Add support for extracting dosage information from the freetext signature for a medication request using the RxParser algorithm developed by University of Utah.

A reference for a recent comparative study using this algorithm:

Approaches for extracting daily dosage from free-text prescription signatures in heart failure with reduced ejection fraction: a comparative study
https://pubmed.ncbi.nlm.nih.gov/39759772/