Add ability to "Favourite" projects

[tom114]

Describe your idea for a new feature

Give users the ability to set a number of projects as their "Favourites". This could give them faster access to those projects without going to the user projects list.

Describe how you would access this feature?

Favourite a project somewhere on the project page. Maybe a :star: in the heading or in the project settings page.

Users could then access their favourited projects on the dashboard or some other convenient interface.

Additional information

The dashboard is getting some new space opened up with the refactors of the announcements in #913. This might be a good replacement for that new whitespace.