Remove underscore logic

There is remaining underscore logic for rules left over from editor. https://github.com/cdisc-org/cdisc-rules-engine/blob/46ef2f2b3e6efd3221bdd34f6b5a3cb31e71d358/cdisc_rules_engine/models/rule.py#L85 This is not needed and it would be good to transition out of it--the parsing logic as well as the references to paramaters with underscores in their names will need to be phased out.

this ticket spurred this one: https://github.com/cdisc-org/cdisc-library-api/issues/16