Move shared code to a new QmlJSTools plugin.

Reviewed-by: Thomas Hartmann

src/libs/qmljs/qmljsmodelmanagerinterface.cpp

@@ -42,6 +42,8 @@ ModelManagerInterface::ModelManagerInterface(QObject *parent)
 
 ModelManagerInterface::~ModelManagerInterface()
 {
+    Q_ASSERT(g_instance == this);
+    g_instance = 0;
 }
 
 ModelManagerInterface *ModelManagerInterface::instance()