Remove a bunch of Python2-related warts (#2315)

* remove all of the "from __future__" imports

* remove the first batch of rdkit.six imports/uses

* next step of rdkit.six removal

* removing xrange, range, and some maps

* next round of removals

* next round of cleanups

* fix inchi test

* last bits of "from rdkit.six" are gone

* and the last of the six stuff is gone

* strange importlib problem

Code/Numerics/Alignment/Wrap/testAlignment.py

@@ -3,7 +3,7 @@
 Replaced numpy.oldnumeric with numpy methods - Jan 2015, PGedeck
 """
 #pylint: disable=E1101,C0111,R0904
-from __future__ import print_function
+
 
 import rdkit.Numerics.rdAlignment as rdAlg
 from rdkit import Geometry