Better handling of namespace validation to fix a number of issues

- Fixes a bug which allows for underscores at the beginning of namespaces: Fixes #1849
- Allows dots and dashes for newer Docker clients: Fixes #1188
- Has the UI display better messaging associated with namespace entry

static/js/directives/ui/namespace-input.js

@@ -0,0 +1,32 @@
+/**
+ * An element which displays an input box for creating a namespace.
+ */
+angular.module('quay').directive('namespaceInput', function () {
+  var directiveDefinitionObject = {
+    priority: 0,
+    templateUrl: '/static/directives/namespace-input.html',
+    replace: false,
+    transclude: true,
+    restrict: 'C',
+    scope: {
+      'binding': '=binding',
+      'isBackIncompat': '=isBackIncompat',
+      'namespaceTitle': '@namespaceTitle',
+    },
+    controller: function($scope, $element) {
+      $scope.USERNAME_PATTERN = USERNAME_PATTERN;
+      $scope.usernamePattern = new RegExp(USERNAME_PATTERN);
+
+
+      $scope.$watch('binding', function(binding) {
+        if (!binding) {
+          $scope.isBackIncompat = false;
+          return;
+        }
+
+        $scope.isBackIncompat = (binding.indexOf('-') > 0 || binding.indexOf('.') > 0);
+      })
+    }
+  };
+  return directiveDefinitionObject;
+});