Tuning cache controls. In Chrome a reload sets the request header to

max-age=0, but still includes an If-None-Match header.  That means we
sould not depend o a cached ETag, which we don't in any case.  A
shift-reload on the other hand sets the header to no-cache and does not
include an If-None-Match header, meaning this is not a conditional get
at all.

src/main/java/org/forkalsrud/album/web/AlbumServlet.java

@@ -445,7 +445,7 @@ public class AlbumServlet
     boolean etagMatches(HttpServletRequest req, String fileEtag) {
 
     	String cacheControl = req.getHeader("Cache-Control");
-    	if ("max-age=0".equals(cacheControl)) {
+    	if ("no-cache".equals(cacheControl)) {
     		return false;
     	}
     	String reqEtag = req.getHeader("If-None-Match");