fix boolean cast from string

* Simply using dtyp of asarray result in all True except for empty

ArchiveExtractor.py

@@ -578,7 +578,11 @@ def _extract_scalar(attribute, method, date1, date2, db, dtype):
 
 
             # Transform to datetime - value arrays
-            _value = np.asarray(_value, dtype=dtype)
+            if dtype is bool:
+                _value = np.asarray([{"true":True, "false":False}[_a.lower()] for _a in _value])
+            else:
+                _value = np.asarray(_value, dtype=dtype)
+
             if len(_date) > 0:
                 _date = _ArrayTimeStampToDatetime(_date/1000.0)