Added mobile browser detection to disable FileReader controls on mobile devices

While support for local disk images and other local resources can work on some mobile devices, I don't think the use cases warrant the extra (largely wasted) screen space

modules/shared/lib/weblib.js

@@ -549,6 +549,20 @@ web.isUserAgent = function(s)
     return false;
 };
 
+/**
+ * isMobile()
+ *
+ * Check the browser's user-agent string for the substring "Mobi", as per Mozilla recommendation:
+ *
+ *      https://developer.mozilla.org/en-US/docs/Browser_detection_using_the_user_agent
+ *
+ * @return {boolean} is true if the browser appears to be a mobile (ie, non-desktop) web browser, false if not
+ */
+web.isMobile = function()
+{
+    return web.isUserAgent("Mobi");
+};
+
 /**
  * getURLParameters(sParms)
  *