Fix ShapeNetDataset (#593)

Summary:
- Add MANIFEST.in and `include_package_data=True` to include dataset .json files in the installation
Fix https://github.com/facebookresearch/pytorch3d/issues/435
- Fix `load_textures=False` for ShapeNetDataset with a test
Fix https://github.com/facebookresearch/pytorch3d/issues/450, partly fix https://github.com/facebookresearch/pytorch3d/issues/444. I've set the textures to `None`, if they should be all white instead, let me know.

Pull Request resolved: https://github.com/facebookresearch/pytorch3d/pull/593

Reviewed By: patricklabatut

Differential Revision: D29116264

Pulled By: nikhilaravi

fbshipit-source-id: 1fb0198e616b7f834dfeaf7168bb5e6e530810d1

tests/test_shapenet_core.py

@@ -282,3 +282,10 @@ class TestShapenetCore(TestCaseMixin, unittest.TestCase):
                 "test_shapenet_core_render_without_sample_nums_%s.png" % idx, DATA_DIR
             )
             self.assertClose(mixed_rgb_2, image_ref, atol=0.05)
+
+    def test_load_textures_false(self):
+        shapenet_dataset = ShapeNetCore(
+            SHAPENET_PATH, load_textures=False, version=VERSION
+        )
+        model = shapenet_dataset[0]
+        self.assertIsNone(model["textures"])