don't allow deleting the current backend
only allow deleting of backends using AJAX
go back to the previous page when changing backends, except if the page
was a movie/TV show details page
check backend connectivity when adding/updating backends (fixes #85)
when adding/updating backends, check that a connectable backend is
actually XBMC and not some other software (fixes #86)
check that the credentials for the backend are valid when
adding/updating backends (fixes #87)
reuse Controller::redirectToPrevious()
remove some unused auto-generated code
minor cosmetics (together with the previous two commits fixes #89)