Catch Up Upstream

[AlexCatarino]

Rebase with pythonnet master.

Most important changes:

• Improved performance of calls from Python to C#
• Added support for converting python iterators to C# arrays
• When calling C# from Python, enable passing argument of any type to a parameter of C# type object by wrapping it into PyObject instance
• Added support for kwarg parameters when calling .NET methods from Python
• Reworked Finalizer. Now objects drop into its queue upon finalization, which is periodically drained when new objects are created.
• PyExport attribute to hide .NET types from Python
• PythonException.Format method to format exceptions the same as traceback.format_exception
• PyObject.IsNone() to check if a Python object is None in .NET.
• Codecs as the designated way to handle automatic conversions between .NET and Python types **
• Fix incorrect dereference in params array handling
• Fix incorrect dereference of wrapper object in tp_repr, which may result in a program crash
• Drop support for Python 2

[codecov-commenter]

Codecov Report

Merging #45 into master will decrease coverage by 4.47%. The diff coverage is 47.36%.

@@            Coverage Diff             @@
##           master      #45      +/-   ##
==========================================
- Coverage   69.42%   64.94%   -4.48%     
==========================================
  Files           1        1              
  Lines         278      291      +13     
==========================================
- Hits          193      189       -4     
- Misses         85      102      +17     

Flag	Coverage Δ
#setup_linux	64.94% <47.36%> (-4.48%)	:arrow_down:

Impacted Files	Coverage Δ
setup.py	64.94% <47.36%> (-4.48%)	:arrow_down:

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[jaredbroad]

Can you please post a summary of the upgrades/fixes?

[Martin-Molinero]

Closing in favor of https://github.com/QuantConnect/pythonnet/pull/47