Add the ability to run a plan as another user

When running a public continuous integration server, the potential risk is that a rogue build will interfere with

1. bamboo
2. another project

While I suspect we could use remote agents to get around most of the risk of a plan interfering with bamboo; it does not help with preventing interference between projects.

A cunning plan that I had was to allow the bamboo server to sudo to a variety of different accounts (typically one user per project.

The launching the build would look something like

sudo -u <project user> /home/bamboo/home/temp/launcher.sh

Then the entire build would run as that user, completely isolated from the rest of the system and other plans.

I've looked through the various plugins, and it doesn't appear I can write a plugin to intercept the build - and I don't want to have to write 4 plugins that pretty much replicate the existing builders (Ant / Maven / Maven2 / bash) - unless I can call them easily after I've sudoed - which I doubt.