async temporal extent integration with ui

 * date picker integration
 * time picker integration
 * more tests for temporal extent
 * ncwms initializes to most recent time after extent loaded
avoiding findLayerAsJson for ncwms

probing temporal extent from geonetwork and deciding whether to
call findLayerAsJson or not
set bbox for layer from geonetwork record

when clicking the zoom button, the interface will know how to zoom on
the layer