DOC: import "numpy for matlab users" from the wiki

Might be useful to someone.

Excised too opinionated parts and replaced most links to specific
software with the topical software page links.

Author: pv

doc/source/user/index.rst

@@ -16,5 +16,6 @@ classes contained in the package, see the :ref:`reference`.
    quickstart
    basics
    misc
+   numpy-for-matlab-users
    building
    c-info