Prefix editor's uniqueId with plugin name

In this way we minimize the chance of
generating non-unique id.

Change-Id: Idd177c5a4b44b17a58c2a944ec77b9517e91964e
Reviewed-by: Eike Ziller <eike.ziller@qt.io>

src/plugins/qmljseditor/qmljseditorconstants.h

@@ -30,6 +30,8 @@
 namespace QmlJSEditor {
 namespace Constants {
 
+const char QML_JS_EDITOR_PLUGIN[] = "QmlJSEditorPlugin";
+
 const char M_CONTEXT[] = "QML JS Editor.ContextMenu";
 
 const char M_REFACTORING_MENU_INSERTION_POINT[] = "QmlJSEditor.RefactorGroup";