Allow editing of project description from the project overview page

Problem

Projects can have descriptions, but the description is managed out of an area in the settings. There are two problems with that:

• Users are not asked to add a description during the creation of a new project. That means they might not even be aware that it is possible to add a description unless they stumble across it in settings. This problem is tackled in this issue: Add a project description during blank project ... (#370469)
• When a user wants to change the description, they have to know that they have to go into settings first, find the appropriate section and then change the description there.

Current project overview page with description:

Current general settings page where the description can be added:

Proposal

Make changing the project description actionable where it appears: in the project overview screen. It could be as simple as indicating that the description field is editable upon hover, or by adding an edit icon.

• Only project owners or maintainers should be able to change the description.
• Users who are not owners or maintainers should not be able to see the interaction to change the description. As they have no access to settings, this is irrelevant to them.
• The ability to change a project description should be removed from the General settings page.
• For project that do not yet have a description, there needs to be an action on the project overview page to add a description if desired. This action would only be available to project owners or maintainers.