Set Environment Variables in Gnome on Ubuntu Linux

On Ubuntu 9.04 (and probably other versions),

1. `/bin/sh /etc/gdm/Xsession default` reads ~/.profile
2. /bin/sh is Dash, not Bash.  Dash accepts a subset of the syntax that Bash accepts.
3. Environment variables set in ~/.profile or in files sourced by ~/.profile are propagated to Gnome and programs launched from Gnome.