QPID-6276: [Java Broker] Disable upload feature (with tooltip to indicate why) in browsers that do not support HTML5

* Also used file icon (rather than tick) to symbolise the fact that file file is loaded client side. The tick gave the
impression that the file was valid.

git-svn-id: https://svn.apache.org/repos/asf/qpid/trunk@1647307 13f79535-47bb-0310-9956-ffa450edef68