Fix spelling of layer manager title

nxt_editor/dockwidgets/layer_manager.py

@@ -19,7 +19,7 @@
 class LayerManager(DockWidgetBase):
     """Interactive tree view of the layers in the open graph.
     """
-    def __init__(self, title='Layer Manger', parent=None):
+    def __init__(self, title='Layer Manager', parent=None):
         super(LayerManager, self).__init__(title=title,
                                            parent=parent,
                                            minimum_width=100)