Remote Terminology Passes Boolean Values through as String Values

When doing CodeSystem Lookups using Remote Terminology, boolean values are returned as valueString in the response

Example Response property:

```
{
  "name": "value",
  "valueString": "BooleanType[true]"
}
```

Expected Response property:

```
{
  "name": "value",
  "valueBoolean": true
}
```

**Environment: 
 - HAPI FHIR Version : v7.6.1
