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/CustomIndicatorAlgorithm.py

@@ -13,13 +13,14 @@
 
 from clr import AddReference
 AddReference("System")
+AddReference("QuantConnect.Algorithm")
 AddReference("QuantConnect.Indicators")
 AddReference("QuantConnect.Common")
 
 from System import *
 from QuantConnect import *
 from QuantConnect.Indicators import *
-from QCAlgorithm import QCAlgorithm
+from QuantConnect.Algorithm import *
 from collections import deque
 from datetime import datetime, timedelta
 from numpy import sum