Support Run via xvfb

I wanted to suggest a new feature in QtCreator, namely a checkbox next to "Run in terminal" that says "Run in xvfb mode".

This way, the executable that is being run will be run behind the scenes, which is sometimes necessary when you are connecting remotely via SSH.

When enabled, the checkbox would automatically pre-pend "xvfb-run " to the executable name.

My workaround for the moment is to go to the run environment and set the DISPLAY to :0.0, however this only works if there is an active session (user logged in the actual machine).