[doc] Add information about CLA and contributing

doc/contribute.rst

+.. -*- coding: utf-8 -*-
+
+.. _bob.ip.binseg.contribute:
+
+===================================
+ Getting Involved and Contributing
+===================================
+
+We will happily accept external contributions, but substantial contributions
+require a signed Contributor or `Copyright License Agreement <cla_>`_ (CLA).
+Our CLA, based on `Project Harmony`_, leaves copyright with you (the
+contributor), but allows us to relicense the code, with a restriction based on
+the license the contribution was made under.
+
+Contact our `Technology Transfer Officer <tto_>`_ to get a copy of the CLA_ for
+this project.  If you work for a company and your contributions are tied to
+your job, ensure you have the legal right to sign this CLA, or refer to the
+responsible person during your e-mail exchange with our TTO_.
+
+
+.. include:: links.rst