Button event signatures fixed for consistency
Button event signatures fixed for consistency

Button event signatures now "handlerMethod(eventSource, eventData)"
where eventData == { button }

daverome/openseadragon,Iced-Tea/openseadragon,mcanthony/openseadragon,shaunstanislaus/openseadragon,openseadragon/openseadragon,LarissaSmith/openseadragon,sul-dlss/openseadragon,mcanthony/openseadragon,TMUND/openseadragon,janelia-flyem/openseadragon,seanich/openseadragon,lidasong2014/openseadragon,avandecreme/openseadragon,avandecreme/openseadragon,ricochet2200/openseadragon,LafayetteCollegeLibraries/openseadragon,openseadragon/openseadragon,msalsbery/openseadragon,ricochet2200/openseadragon,seanich/openseadragon,goofwear/openseadragon,rdlester/openseadragon,daverome/openseadragon,lidasong2014/openseadragon,jmnetus/openseadragon,janelia-flyem/openseadragon,msalsbery/openseadragon,shaunstanislaus/openseadragon,rdlester/openseadragon,TMUND/openseadragon,goofwear/openseadragon,LarissaSmith/openseadragon,Iced-Tea/openseadragon,jmnetus/openseadragon