Fix gltf static mesh loading issues (#14)

* Support u8 / u32 indices

* Skip primitives without vertices

* Add support for non-indexed geometry & skipping primitives

* Fix possible memory leak on error

* Use SSkinnedMesh

* Check indices

* Properly mirror node hierarchy

* Update .gitignore

* Reorder includes

* Add some throws for logic errors

* Fix non-indexed geometry winding order, add unit test

* Address code review comments

* Add matrix transform unit test

source/Irrlicht/tests/assets/triangle_without_indices.gltf

@@ -0,0 +1,54 @@
+{
+  "scene" : 0,
+  "scenes" : [
+    {
+      "nodes" : [ 0 ]
+    }
+  ],
+  
+  "nodes" : [
+    {
+      "mesh" : 0
+    }
+  ],
+
+  "meshes" : [
+    {
+      "primitives" : [ {
+        "attributes" : {
+          "POSITION" : 0
+        }
+      } ]
+    }
+  ],
+
+  "buffers" : [
+    {
+      "uri" : "data:application/octet-stream;base64,AAAAAAAAAAAAAAAAAACAPwAAAAAAAAAAAAAAAAAAgD8AAAAA",
+      "byteLength" : 36
+    }
+  ],
+  "bufferViews" : [
+    {
+      "buffer" : 0,
+      "byteOffset" : 0,
+      "byteLength" : 36,
+      "target" : 34962
+    }
+  ],
+  "accessors" : [
+    {
+      "bufferView" : 0,
+      "byteOffset" : 0,
+      "componentType" : 5126,
+      "count" : 3,
+      "type" : "VEC3",
+      "max" : [ 1.0, 1.0, 0.0 ],
+      "min" : [ 0.0, 0.0, 0.0 ]
+    }
+  ],
+  
+  "asset" : {
+    "version" : "2.0"
+  }
+}