Add CWLVersions to draft-2, and change cwlVersion field to ref CWLVersions enum

instead.

Author: Peter Amstutz

draft-2/CommonWorkflowLanguage.yml

@@ -587,6 +587,11 @@ $graph:
   type: documentation
   doc: This section specifies the core object types that make up a CWL document.
 
+- type: enum
+  name: CWLVersions
+  doc: "Version symbols for published CWL document versions."
+  symbols:
+    - cwl:draft-2
 
 - name: Datatype
   type: enum
@@ -1066,13 +1071,12 @@ $graph:
     - name: cwlVersion
       type:
         - "null"
-        - string
+        - "#CWLVersions"
       doc: "CWL document version"
       jsonldPredicate:
         "_id": "cwl:cwlVersion"
         "_type": "@vocab"
 
-
 - type: record
   name: CommandLineBinding
   extends: "#Binding"

draft-3/Process.yml

@@ -25,6 +25,7 @@ $graph:
   name: CWLVersions
   doc: "Version symbols for published CWL document versions."
   symbols:
+    - cwl:draft-2
     - cwl:draft-3.dev1
     - cwl:draft-3.dev2
     - cwl:draft-3.dev3
@@ -507,7 +508,7 @@ $graph:
     - name: cwlVersion
       type:
         - "null"
-        - string
+        - "#CWLVersions"
       doc: "CWL document version"
       jsonldPredicate:
         "_id": "cwl:cwlVersion"

draft-4/Process.yml

@@ -24,6 +24,7 @@ $graph:
   name: CWLVersions
   doc: "Version symbols for published CWL document versions."
   symbols:
+    - cwl:draft-2
     - cwl:draft-3.dev1
     - cwl:draft-3.dev2
     - cwl:draft-3.dev3
@@ -545,7 +546,7 @@ $graph:
     - name: cwlVersion
       type:
         - "null"
-        - string
+        - "#CWLVersions"
       doc: "CWL document version"
       jsonldPredicate:
         "_id": "cwl:cwlVersion"