[ntcore] Various fixes (#4469)

* Fix C++ Publisher and Subscriber move assignment 
* Fix Publisher comment typo.
* Publish: check that properties is an object.
Print a warning, but still publish, just with empty properties.
Add error print for unassigned type publish.
* Return boolean from SetProperties
* Document exception-throw in Java for invalid JSON.

ntcore/src/generate/java/Topic.java.jinja

@@ -136,6 +136,7 @@ public final class {{ TypeName }}Topic extends Topic {
    * @param properties JSON properties
    * @param options publish options
    * @return publisher
+   * @throws IllegalArgumentException if properties is not a JSON object
    */
   public {{ TypeName }}Publisher publishEx(
       String typeString,