Add a displayOrder variable to WebUITab to specify the order in which tabs appear

Add a displayOrder variable to WebUITab to specify the order in which tabs appear. Currently, the tabs are ordered by when they get attached, which isn't always desired. The default is MIN_VALUE, meaning if it's not specified, it will appear in the order added before any tabs with a non-default displayOrder.  For example, we would like to have the SQL Tab appear before the Connect tab; however, based on the code flow, the Connect tab will be attached first and with the current logic, that tab would also appear first.