Produce benchmark JSON schema v2

- No more '(Display)' strings in the GPU names, but store devices as
  `{'name': name, 'type': 'CPU/CUDA/OPENCL', 'is_display': bool}`
- Introduces testing with py.test & pipenv. The test suite is far from
  complete, though.

.gitignore

@@ -14,3 +14,7 @@ __pycache__
 /bundle/blender-benchmark-*.dmg
 /bundle/blender-benchmark-*.tar.bz2
 /bundle/blender-benchmark-*.zip
+
+.cache
+.coverage
+.pytest_cache/