Add query planning for target environments

[brynrhodes]

CQL is a platform-independent query representation, and may be evaluated in different environments. The most efficient evaluation strategy often depends on the capabilities of target environments, resulting in the need for a query planning step that considers target environments.

Specifically, initial capabilities need to support:

1. Optimizations for date range (translator issues 544, 545, and 546)
2. Include optimizations for medication references from a MedicationRequest resource.
3. Rewrite of primary code path for a retrieve based on capabilities (code vs category in MedicationRequest)