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/CustomBenchmarkAlgorithm.py

@@ -13,11 +13,12 @@
 
 from clr import AddReference
 AddReference("System")
+AddReference("QuantConnect.Algorithm")
 AddReference("QuantConnect.Common")
 
 from System import *
 from QuantConnect import *
-from QCAlgorithm import QCAlgorithm
+from QuantConnect.Algorithm import *
 
 ### <summary>
 ### Shows how to set a custom benchmark for you algorithms