Allow a repository or project to be archived

To decrease clutter and preserve the state of a repository at the time work was completed, it would be useful to be able to archive a repository or project. An archived project/repo may be hidden from lists and search results by default, indicate its archived status and/or would be read only.

One possible workaround for managing the access side of things is to make the whole project readonly, and then use repository permissions to grant additional access to certain repositories, but this means editing all repositories just to reduce access to one.