protected Toolbar createMainToolbar()
{
Toolbar toolbar = new Toolbar();
toolbar.addLeftWidget(commands_.loadWorkspace().createToolbarButton());
toolbar.addLeftWidget(commands_.saveWorkspace().createToolbarButton());
toolbar.addLeftSeparator();
toolbar.addLeftWidget(createImportMenu());
toolbar.addLeftSeparator();
toolbar.addLeftWidget(commands_.clearWorkspace().createToolbarButton());
toolbar.addLeftSeparator();
toolbar.addLeftWidget(commands_.refreshEnvironment().createToolbarButton());