Cleanup features and check if everything has a solution

Merged Achilleas Pipinellis requested to merge test-feature-solution into master

Since we added the solution categories, some features were missing from the features page.

The added raketask ensures that every feature has a solution assigned to it.

Related issue: https://gitlab.com/gitlab-com/www-gitlab-com/issues/1572

Edited by Achilleas Pipinellis