set cwlVersion as mandatory for draft-4

Author: mr-c

draft-4/Process.yml

@@ -715,8 +715,7 @@ $graph:
       doc: "A long, human-readable description of this process object."
     - name: cwlVersion
       type:
-        - "null"
-        - "#CWLVersions"
+        - CWLVersions
       doc: "CWL document version"
       jsonldPredicate:
         "_id": "cwl:cwlVersion"

draft-4/invocation.md

@@ -109,7 +109,7 @@ not perform computation on the contents.
   * `runtime.outdir`: an absolute path to the designated output directory
   * `runtime.tmpdir`: an absolute path to the designated temporary directory
   * `runtime.cores`:  number of CPU cores reserved for the tool process
-  * `runtime.ram`:    amount of RAM in mebibytes (2**20) reserved for the tool process
+  * `runtime.ram`:    amount of RAM in mebibytes (2\*\*20) reserved for the tool process
   * `runtime.outdirSize`: reserved storage space available in the designated output directory
   * `runtime.tmpdirSize`: reserved storage space available in the designated temporary directory