[#1117] Add factory_boy to action tests

Add a new module ckan.new_tests.factories with (so far) just a User factory
class that uses the factory_boy library to create CKAN users.

Update the ckan.new_tests.logic.action.test_update tests to use this
factory instead of ckan.new_tests.data.

Still need to update the rest of the new tests to use the factory (and
also add factories for other classes such as dataset etc.), then data.py
can be deleted.

Still need to add factory_boy to dev-requirements.txt.
[#1117] Use factory in auth/test_update.py

Instead of data.py.
[#1117] Remove data.py from test_validators.py

Move the helper functions it was using into factories.py and make it use
that instead.
[#1117] Use factories instead of data in navl/test_validators.py

So data.py is now unused and we can remove it.
[#1117] Add some helper decorators to validators tests

Add a bunch of helper decorators at the top of the file, and change the
test methods below to use them.
Merge branch '1117-factory_boy' into 1117-start-new-test-suite