[#1801] Fix test_documentation exit code.


Problem description
===================

When test_documentation was run, it did not exited with the right exit code on failure.


Why we got into this (5 whys)
=============================

There was no test.


Changes description
===================

Update lint and test_documentation task to raise BuildFailure and so to trigger an exit code 1.

Also added a minimum documentation project to manually test that thing work.


How to try and test the changes
===============================

reviewers @alibotean 

Change documentation/index.rst to invalid value ... example have ===== shorter than the title.

Run paver test_os_independent and paver test_documentation and check that the exit code is 1 on failures and 0 on success.

Thanks!