Automate change to run.display=-1 in .processing/preferences.txt

[rturknett]

By default, Processing launches the sketch window on display 0. In order to support MPE configurations that have multiple graphics cards per host (e.g. Stallion).

To do this, the user must change the run.display variable in ~/.processing/preferences.txt:

change
run.display=0
to
run.display=-1

We should add code to modify this setting automatically on each remote system when the user launches an MPE sketch. We should also change the setting back before the Processing sketch exits. Note that the location of the user's .processing file may be different on Linux, Windows, and OSX.