Enhanced stereo read/write support in SDF files. (#2022)

* add a couple test files

* backup

* first pass at some theory documentatin

* it's a draft

* Update enhanced stereochemistry documentation

Adds initial target use case and caveats about the tentative
nature of the current implementation.

* Support read/write of molfile enhanced stereochemistry

This includes reading and writing of enhanced stereochemistry
from v3000 molfiles (sdf). Enhanced stereochemistry encodes
the relative configuration of stereocenters, allowing
representation of racemic mixtures and compounds with
unknown absolute stereochemistry.

It does not include:
* Python wrapping
* invalidation of the enhanced stereochemistry
* use of enhanced stereochemistry in search
* depiction of enhanced stereochemistry.

* Update to reflect changes from #1971

* change names of enum elements to allow compilation in VS2017

I think it's also clearer to do things this way

* Addressed most review comments.

* Run missed test "testEnhancedStereoChemistry"
* In tests, added size checks to group equality checks
* Updated copyright statements
* Deleted mol created for a test
* Use perfect forwarding in RWMol::setStereoGroups()
* use references for stereo groups that are checked in write and pickle
* Updated stereogroup.h in hopes of fixing compilation on Windows.
* clang-format

* try allowing a switch to boost regex and requiring it for g++-4.8

* do a better job of that

* typo

* Code review comments. Updated Copyright notice.

* When an atom is deleted, delete stereo groups containing it.

Also updates StereoGroup toUse accessors instead of
constant member attributes. This allows move of StereoGroups.

* RDKit style guide

* Add header required on Windows.

* get the SWIG wrappers to build

Code/JavaWrappers/csharp_wrapper/GraphMolCSharp.i

@@ -1,6 +1,5 @@
 
 /*
-* $Id: GraphMolJava.i 2141 2012-07-27 06:16:45Z glandrum $
 *
 *  Copyright (c) 2010, Novartis Institutes for BioMedical Research Inc.
 *  All rights reserved.
@@ -207,6 +206,7 @@ typedef unsigned long long int	uintmax_t;
 %include "../Conformer.i"
 %include "../Dict.i"
 %include "../RDProps.i"
+%include "../StereoGroup.i"
 %include "../ROMol.i"
 %include "../RWMol.i"
 %include "../Bond.i"