Close #19407: New installation & distribution guides

- based on pip and other PyPA tools
- includes references to the new Python Packaging User Guide
  where appropriate (and the relevant section is at least
  partially filled in)
- started new FAQ sections
- both guides aim to introduce users to basic open source
  concepts if they aren't aware of them
- existing guides have been relocated (now linked from the
  distutils docs) rather then removed, since there is
  some needed material that has yet to be relocated to the
  distutils docs as a reference for the legacy formats

Doc/using/venv-create.inc

@@ -11,6 +11,11 @@ containing a copy of the ``python`` binary (or binaries, in the case of
 Windows).  It also creates an (initially empty) ``lib/pythonX.Y/site-packages``
 subdirectory (on Windows, this is ``Lib\site-packages``).
 
+.. seealso::
+
+   `Python Packaging User Guide: Creating and using virtual environments
+   <http://packaging.python.org/en/latest/tutorial.html#creating-and-using-virtual-environments>`__
+
 .. highlight:: none
 
 On Windows, you may have to invoke the ``pyvenv`` script as follows, if you