Provide support for project groups. #68
Description
We have these over on thimble.webmaker.org (https://thimble.webmaker.org/en-US/webarcade and https://thimble.webmaker.org/en-US/projects/zoo) but don't have them on webmaker.org.
We need to include the ability to:
- create a new project group with a custom HTML template, CSS (to be included via a pull request)
- assign projects to a group
- create a groups view - rendering the template provided and listing all projects assigned to the group
- allow a way for a project to return what groups it belongs to
- allow for ordering of projects within a group