Allow browsing skills by category #159
Description
As an OSMT user, I'd like to be able to browse a skills collection by metadata.
Include a new category detail page showing all skills in a category. Add a new category list page in which the Category would be a hyperlink. The link would take the user to the new category detail page showing all skills in a category.
Similar functionality would be nice to add for Keywords and Occupations. (separate issue/PR)