Allow base url to be specified on a per-project or space basis

This is actually for Confluence! But the only available project was JIRA, even from Confluence's JIRA page.

I have several spaces that I manage on my installation. Each is for a different client. I have my web server configured to have a separate URL for each of the clients, so that they have a URL specific to their installation. This is important to give clients a separation between their projects. It's also important on projects where I work as a subcontractor and I can't directly give access to my own company's URL; I have to appear to be working for another company. This is critical for some of my clients.

You can adjust a space to handle different base urls for email, but you can't adjust the base URL for the installation itself. If I have a base URL, regardless of how I configure my web server to point at the installation, the links for things like logout, spaces, etc., always use the base URL for the installation. Just as you can adjust the base URL for email from a space, it would be great (and essential, in my case) if you could adjust the base URL so that in each space, the base URL for the app-wide links like login/logout would change.

Note that I've used the words "project" and "space" interchangeably above.