initial commit of expression classes
Update CMS146 example to be valid against current grammar
Add initial intermediate models for high-level CqlLibrary, DataRetrieve, and ValueSet-- along with corresponding visitor and trackback classes.
Update antlr4 dependency to 4.3, introduce stringtemplate dependency
adding toCql method
Renamed DataRetrieve to SourceDataCriteria
Update SourceDataCriteria to use QualifiedIdentifier and IdentifierExpression; fix ValueSet in grammar to use a STRING
merging from github
Refactor RetrieveExpression to use SourceDataCriteria
adding trackback info to Expression to identify the expressions within the source document.  Added stubbed out evaluate method to expression for creating a simple poc runtime.  Added Context and callable interfaces for enabling poc runtime evaluation
adding Trackable assertions to existing expression tests to ensure that they each receive a trackback object and a uuid
merging from github repo.  Reformated code to make it more consistent and organized the imports to eliminate unused imports
fixing bug that was introduced during merge where dataCriteria was not set on the RetrieveExpression
Remove quotes from STRING and VALUESET when parsing, make trackable use 1-based char index, add test for CMS146 parsing
Fixed trackbacks for variables, added tests.
merge from master
Update CQL-to-Javascript translator for changes to CQL grammar.
Merge remote-tracking branch 'origin/master' into cql_execution
Initial attempt at using ELM as an intermediate model for CQL execution-- still very incomplete
Added scratchpad to examples.