Bz1031156

Couldn't eliminate the fuse camel route editor from the workbench/ project explorer pull-down since it was registered by supported extension (xml) and the OpenWithMenu method was not extendable.  No other supported was to exclude a partucular file.  Consequently - added a check to the RiderDesignEditor to issue a warning if it encounters a 'switchyard.xml' file and then default to the source editor (design editor is always empty).  The source editor will work.