hub: Allow deleting a project from the client UI

[elisee]

My personal bias would go towards only unloading the project from the server and renaming its folder on disk to something like ${projectSlug}.deleted (Project folder names containing dots are ignored when the server starts up), rather than deleting it altogether, because that would be an irreversible operation and it's safest if people do it through familiar channels like their Explorer/Finder or shell.

I think until authentication and access rights as laid out in #55 are in, we should only enable it for passwordless local-only servers (because letting anyone with the server password delete projects seems like too much power).