Kill the bad things

[cmoesel]

This PR removes support for formerly deprecated syntax features, including:

• Mixins: keyword
• units keyword
• , path separator in flag rules (replaced by and)
• , concept separator in value set rules (replaced by and)
• | type separator in references (replaced by or)

These have all been removed from the formal grammar (to keep it nice and tidy). When ANTLR produces syntax errors, SUSHI analyzes them to produce a friendly error message.

Tests have been updated accordingly, but you can also test this manually with the following FSH:

Profile: MyPatient
Parent: Patient
// Mixins == bad
Mixins: MyRS
* name 1..* MS

RuleSet: MyRS
* active MS

Profile: MyObservation
Parent: Observation
// units == bad
* valueQuantity units = http://foo.org#bar

Alias: MyVS = http://boo.org/far

Profile: MyObservation2
Parent: Observation
// units == bad
* valueQuantity units from MyVS (preferred)

Profile: MyCondition
Parent: Condition
// , == bad
* onset[x], abatement[x] MS

Alias: Zoo = http://zoo.org
ValueSet: MyValueSet
// , == bad
* #hippo, #crocodile , #emu from system Zoo

ValueSet: MyValueSet2
// , == bad
* codes from valueset FirstZooVS, SecondZooVS

ValueSet: FirstZooVS
* Zoo#foo

ValueSet: SecondZooVS
* Zoo#bar

Extension: MyExtension
// | == bad
* value[x] only Reference(Patient | Practitioner | Person)

[cmoesel]

Also... hurray for deleting code!

[jafeltra]

Looks great! I got the expected errors and the tests look updated to me!

I haven't run the regression script on this yet, but I can if we'd like before officially merging.

[cmoesel]

I ran the regression:all script and there were (surprisingly) no regressions. I guess our warnings about deprecated syntax worked! So... I am going to merge.