[bugfix] fix NPE
[bugfix] change order of items
[feature] added headline at wherigo main menu
[improve] add method attach() and dettach()
[improve] implement attach() and dettach() for register/unregister
(remove TODO comments)
[bugfix] wherigo main menu items are not refreshed
[feature] icon at ListItemHeader, added cartridge icon at Wherigo main
menu header
[bugfix] a second 'navigate' button is shown at wherigo details activity
[bugfix] remove self-assignment
[bugfix] commit forgotten file