C# decimal to Python conversion

- This commit is related to PR 19 in QC/pythonnet
   - C# decimal will be cast to C# double and converted into python
   float
- Adding new `decimal.py` into the python algorithm project. This is
required for backwards compatibility with users performing operations
over expected decimal types (like `Price`)
- Updating two python regression test algorithms using custom python
execution models to be aware and ignore floating point precision errors
when handling order sizing.

Algorithm.Python/QuantConnect.Algorithm.Python.csproj

@@ -41,6 +41,7 @@
     <Content Include="BasicTemplateFuturesFrameworkAlgorithm.py" />
     <Content Include="BasicTemplateOptionsFrameworkAlgorithm.py" />
     <Compile Include="Properties\AssemblyInfo.cs" />
+    <Content Include="decimal.py" />
     <None Include="CompositeRiskManagementModelFrameworkAlgorithm.py" />
     <None Include="BlackLittermanPortfolioOptimizationFrameworkAlgorithm.py" />
     <None Include="packages.config" />