Upgrade NAS-API to v2.0:

we use an abstract class NASBenchMetaAPI to define the spec of an API; it can be inherited to support different kinds of NAS API, while keep the query interface the same.

exps/experimental/test-api.py

@@ -0,0 +1,20 @@
+# 
+# exps/experimental/test-api.py
+#
+import sys, time, random, argparse
+from copy import deepcopy
+import torchvision.models as models
+from pathlib import Path
+lib_dir = (Path(__file__).parent / '..' / '..' / 'lib').resolve()
+if str(lib_dir) not in sys.path: sys.path.insert(0, str(lib_dir))
+
+from nas_201_api import NASBench201API as API
+
+
+def main():
+  api = API(None)
+  info = api.get_more_info(100, 'cifar100', 199, False, True)
+
+
+if __name__ == '__main__':
+  main()