Added CardinalAxis and FlattenMode enum definitions (#261)

* Added CardinalAxis and FlattenMode enum definitions

* removes specific language to bounding box

Definitions/Utilities/CardinalAxis.cs

@@ -0,0 +1,22 @@
+// Copyright (c) XRTK. All rights reserved.
+// Licensed under the MIT License. See LICENSE in the project root for license information.
+
+using System;
+
+namespace XRTK.Definitions.Utilities
+{
+    /// <summary>
+    /// Enum which describes cardinal axes
+    /// </summary>
+    [Flags]
+    public enum CardinalAxis
+    {
+        // Note: Because of the way Unity handles flags
+        // We didn't add a default enum definition nor everything.
+        // Everything = -1
+        // None = 0,
+        X = 1,
+        Y = 2,
+        Z = 3,
+    }
+}

Definitions/Utilities/FlattenMode.cs

@@ -0,0 +1,29 @@
+// Copyright (c) XRTK. All rights reserved.
+// Licensed under the MIT License. See LICENSE in the project root for license information.
+
+namespace XRTK.Definitions.Utilities
+{
+    /// <summary>
+    /// Enum which describes how an object is to be flattened.
+    /// </summary>
+    public enum FlattenMode
+    {
+        DoNotFlatten = 0,
+        /// <summary>
+        /// Flatten the X axis
+        /// </summary>
+        FlattenX,
+        /// <summary>
+        /// Flatten the Y axis
+        /// </summary>
+        FlattenY,
+        /// <summary>
+        /// Flatten the Z axis
+        /// </summary>
+        FlattenZ,
+        /// <summary>
+        /// Flatten the smallest relative axis if it falls below threshold
+        /// </summary>
+        FlattenAuto,
+    }
+}