examples/deepzoom: allow zooming out to view the entire image

After an image was zoomed in to fill the viewport, OpenSeadragon 3.0.0
was allowing zooming out again only until the first pair of image edges
was reached.  Update the configuration to allow zooming out to view the
entire image.

Author: bgilbert

examples/deepzoom/templates/slide-fullpage.html

@@ -37,7 +37,7 @@
         blendTime: 0.1,
         constrainDuringPan: true,
         maxZoomPixelRatio: 2,
-        minZoomLevel: 1,
+        minZoomImageRatio: 1,
         visibilityRatio: 1,
         zoomPerScroll: 2,
         timeout: 120000,

examples/deepzoom/templates/slide-multipane.html

@@ -124,7 +124,7 @@ <h1>Slide properties</h1>
         blendTime: 0.1,
         constrainDuringPan: true,
         maxZoomPixelRatio: 2,
-        minZoomLevel: 1,
+        minZoomImageRatio: 1,
         visibilityRatio: 1,
         zoomPerScroll: 2,
     });