Comment 2 for bug 322469

Added middle click support for launching a new instance of a application that's already running (even if it isn't, middle-click will launch an instance).

Not going to add to menu as we can't always be sure that an application has a window associated with it (requires going through all the windows every time), and the wording would be weird..."Launch new instance", "Launch another instance", "Launcher second instance"?

Windows opened outside of the launcher aren't dealt with currently as it's a bit tricky to get that right. However, going to file a bug about it and attempt to fix it next week.