Better build dialog UX

We now automatically validate the chosen Dockerfile/archive, and automatically check to see if a robot is needed

static/js/directives/file-present.js

@@ -15,4 +15,23 @@ angular.module('quay').directive("filePresent", [function () {
       });
     }
   }
+}]);
+
+/**
+ * Raises the 'filesChanged' event on the scope if a file on the marked <input type="file"> exists.
+ */
+angular.module('quay').directive("filesChanged", [function () {
+  return {
+    restrict: 'A',
+    scope: {
+      'filesChanged': "&"
+    },
+    link: function (scope, element, attributes) {
+      element.bind("change", function (changeEvent) {
+        scope.$apply(function() {
+          scope.filesChanged({'files': changeEvent.target.files});
+        });
+      });
+    }
+  }
 }]);