Reverting 'Merge pull request #2483 python-history-provider'

We didn't experience the expected performance improvements. Locally under
unit test there was aboout an order of magnitude throughput increase, but
when run against the history benchmark, this new approach was 60% slower.
We're reverting this for now to perform further analysis and better
understand the performance profiling of the python history stack.

Algorithm.Python/CustomDataRegressionAlgorithm.py

@@ -14,12 +14,13 @@
 from clr import AddReference
 AddReference("System.Core")
 AddReference("QuantConnect.Common")
+AddReference("QuantConnect.Algorithm")
 
 from System import *
 from QuantConnect import *
+from QuantConnect.Algorithm import QCAlgorithm
 from QuantConnect.Data import SubscriptionDataSource
 from QuantConnect.Python import PythonData
-from QCAlgorithm import QCAlgorithm
 
 from datetime import datetime
 import decimal