These internal functions aid the main functions used in the parsing process
(parseMedExtractR, parseMedXN,
parseMedEx, parseCLAMP).
medxnColonFormat: converts entity information into the
form "extracted expression::start position::stop position", similar
to how output is formatted by default in MedXN output.
entorder: a helper function that orders the entities by start position
medxnEntityFormat: a helper function that applies both medxnColonFormat
to convert entities into the "extraction::start::stop" format and entorder to
sort them. It then collapses the entities and separates the extractions with backticks