ST6RI-178 Fixed non-stanrad library download in Jupyter

 - in the current implementation it is necessary to store
 proxy elements for the standard library
 - these proxy elements also count as root elements
 - the download logic skips these elements when processing root
 - when a LibraryPackage is uploaded form Jupyter it will also count as
a root, so the download logic skips them

 To solve this issue this commit enables non-standard library elements
as root elements during the download process

Author: TheKorpos

org.omg.sysml/src/org/omg/sysml/util/repository/EMFModelRefresher.java

@@ -77,7 +77,7 @@ public EMFModelDelta create() {
 
 		//traverse containment
 		for (var projectRoot: model.getModelRoots().values()) {
-			if (!Boolean.TRUE.equals(projectRoot.get("isLibraryElement"))) {
+			if (isNonStandardLibrary(projectRoot) || !Boolean.TRUE.equals(projectRoot.get("isLibraryElement"))) {
 				EObject rootNamespace = transform(projectRoot);
 				rootNamespaces.put(rootNamespace, projectRoot);
 			}
@@ -97,6 +97,10 @@ public EMFModelDelta create() {
 		return new EMFModelDelta(rootNamespaces);
 	}
 
+	private boolean isNonStandardLibrary(Element element) {
+		return element.get("@type").equals("LibraryPackage") && !Boolean.TRUE.equals(element.get("isStandard"));
+	}
+	
 	private EObject transform(Element dto) {
 		Object uuid = dto.get("@id");