Undo __future__ import for type annotations, which is incompatible with python 3.6

expected to close #20 (closed): Rolling back the import of annotations from __future__ due to being incompatible with python 3.6

armarx_core/time/duration.py

@@ -13,7 +13,7 @@ MIN_LONG_CPP = -9223372036854775808
 
 @dataclasses.dataclass
 class Duration(AronDataclass):
-    microSeconds: np.int64 = MIN_LONG_CPP,   # std::numeric_limits<long>::min()
+    microSeconds: np.int64 = MIN_LONG_CPP   # std::numeric_limits<long>::min()
 
     @staticmethod
     def from_seconds(seconds: float) -> "Duration":