Fix validation of modules with no data set

Previously if the data_group and data_type were set but empty it would
fail with not being able to find the data set. As @timmow suggested, be
liberal in what you accept and conservative in what you emit.
Merge pull request #235 from alphagov/fix-module-with-no-data-set

Fix validation of modules with no data set
Do not cache module type or node list endpoints

The endpoints that are just going to be used by the admin app, we do not
want to cache.
Merge pull request #236 from alphagov/do-not-cache-node-list-pages

Do not cache module type or node list endpoints
Spotlight config json migrated to stagecraft

Includes a test in tools to verify this - it will loop through spotlight
configs and load spotlightified dashboard json for each. It will then
diff them and report on any differences in the imported models.
Token option and use correct environment hostname

Add an option to pass a token and use the environment hostname from
django settings rather than hardcoding both assuming the dev machine.
Get signon token from settings
Skip no-realistic dashboard

Now we validate modules, this contains invalid modules. But we
dont care about it anyway, so skip it
Allow module description to be blank

Some modules have an empty description - this wasnt picked up earlier
because we were not validating modules.
Use HTTPS rather than http

HTTP works on the dev vm but in "real" environments we use HTTPS -
posting over HTTPS will return a 301 which results in a get request
being made.