Update db_dvc (#290)

This commit updates db_dvc by running the script
scripts/standardize_database.py and adding back `ref_material` for
`UniformWater` and `UniformTissue`. Furthermore, the following non-jpg
files were removed from the photocollections/ in db_dvc, as
photocollections should not contain files of the following kind:

```sh
db_dvc/subjects/soren/sessions/test session/photocollections/Soren_repeat_2/texture_1001.exr
db_dvc/subjects/soren/sessions/test session/photocollections/Soren_repeat_2/texture_1002.exr
db_dvc/subjects/soren/sessions/test session/photocollections/Soren_repeat_2/texturedMesh.mtl
db_dvc/subjects/soren/sessions/test session/photocollections/Soren_repeat_2/texturedMesh.obj
db_dvc/subjects/soren/sessions/test session/photocollections/Soren_repeat_3/texture_1001.exr
db_dvc/subjects/soren/sessions/test session/photocollections/Soren_repeat_3/texture_1002.exr
db_dvc/subjects/soren/sessions/test session/photocollections/Soren_repeat_3/texturedMesh.mtl
db_dvc/subjects/soren/sessions/test session/photocollections/Soren_repeat_3/texturedMesh.obj
db_dvc/subjects/soren/sessions/test session/photocollections/Soren_repeat_4/texture_1001.exr
db_dvc/subjects/soren/sessions/test session/photocollections/Soren_repeat_4/texture_1002.exr
db_dvc/subjects/soren/sessions/test session/photocollections/Soren_repeat_4/texturedMesh.mtl
db_dvc/subjects/soren/sessions/test session/photocollections/Soren_repeat_4/texturedMesh.obj
db_dvc/subjects/soren/sessions/test session/photocollections/Soren_repeat_5/texture_1001.exr
db_dvc/subjects/soren/sessions/test session/photocollections/Soren_repeat_5/texture_1002.exr
db_dvc/subjects/soren/sessions/test session/photocollections/Soren_repeat_5/texturedMesh.mtl
db_dvc/subjects/soren/sessions/test session/photocollections/Soren_repeat_5/texturedMesh.obj
```

Author: arhowe00

db_dvc.dvc

@@ -1,5 +1,6 @@
 outs:
-- md5: f71ffee9b653040af1ff5b4a24a889b5.dir
-  nfiles: 813
+- md5: b7b8aea2669121775f0de4df5d046d6e.dir
+  nfiles: 797
   hash: md5
   path: db_dvc
+  size: 2357261179