Add "change priority" label.

Add a label next to the "move up" / "move down" buttons in the
ExplanationPreferencesGeneralPanel dialog, to hopefully make it clearer
that the order of the listed explanation services matters.

protege-editor-owl/src/main/java/org/protege/editor/owl/ui/explanation/ExplanationPreferencesGeneralPanel.java

@@ -108,6 +108,7 @@ private void addUpDownButtons(PreferencesLayoutPanel panel, JTable pluginTable)
 		buttonDown.setEnabled(pluginTable.getSelectedRow() != -1);
 
 		JPanel buttonsUpDown = new JPanel();
+		buttonsUpDown.add(new JLabel("Change priority"));
 		buttonsUpDown.add(buttonUp);
 		buttonsUpDown.add(buttonDown);
 		panel.addGroupComponent(buttonsUpDown);