Fix Context.childContext(null) to default to empty context_values obj…

…ect (#282)

* Fix Context.childContext to default to {} on undefined AND null

Fixes #277

* Context type updates & UnfilteredContext bug fix

Updated Context constructor to indicate that a Library can be passed in as the parent.  Updated PatientContext and UnfilteredContext library property to indicate it is, in fact, a Library. In the process of doing this, discovered code that was looking for expression identifiers at the root of the Library object instead of Library.expressions.  Oops!  Fixed it.

* Upgrade gradle wrapper

* npm audit fix + npm install --save-dev mocha@latest

examples/browser/cql4browsers.js

@@ -8251,7 +8251,7 @@ class UnfilteredContext extends Context {
     rootContext() {
         return this;
     }
-    async findRecords(_template) {
+    findRecords(_template) {
         throw new exception_1.Exception('Retrieves are not currently supported in Unfiltered Context');
     }
     getLibraryContext(_library) {

src/runtime/context.ts

@@ -1,10 +1,10 @@
+import * as dt from '../datatypes/datatypes';
 import { Exception } from '../datatypes/exception';
+import { Library } from '../elm/library';
+import { PatientObject, RetrieveDetails, TerminologyProvider } from '../types';
+import { Parameter } from '../types/runtime.types';
 import { typeIsArray } from '../util/util';
-import * as dt from '../datatypes/datatypes';
 import { MessageListener, NullMessageListener } from './messageListeners';
-import { Parameter } from '../types/runtime.types';
-import { PatientObject, RetrieveDetails, TerminologyProvider } from '../types';
-import { Library } from '../elm/library';
 
 export class Context {
   // Public Constructor args
@@ -482,7 +482,7 @@ export class UnfilteredContext extends Context {
     return this;
   }
 
-  async findRecords(_template: any) {
+  findRecords(_template: any) {
     throw new Exception('Retrieves are not currently supported in Unfiltered Context');
   }