add dep for libgconf for rpi
A user reported the following after trying to run a freshly installed Purr Data deb on RPI:
pi@raspberrypi:~ $ pd-l2ork guidir is /usr/lib/pd-l2ork/bin priority 6 scheduling enabled. priority 8 scheduling enabled. /usr/lib/pd-l2ork/bin/nw/nw: error while loading shared libraries: libgconf-2.so.4: cannot open shared object file: No such file or directory watchdog: signaling pd... watchdog: signaling pd... watchdog: signaling pd...
So we should probably put libgconf as a dependency in the deb