…ackages

gnome-session inherits GDMS PATH, which is at the moment non-functional. In X11
this didn't matter as the `Xsession` wrapper would populate the environment
beforehand. Wayland sessions doesn't source `Xesssion` (duh), so we patch
`bin/gnome-session` to use absolute paths for `grep` and `bash`.

In addition `bin/gnome-session` is a simple wrapper around
`libexec/gnome-session-binary` mostly responsible for sourcing the users profile
before launching the binary. This made our wrapping of `bin/gnome-session`
ineffective on wayland as the profile would reset the environment. Simply wrap
`libexec/gnome-session-binary` instead.

LightDM is unable to separate between `wayland-sessions/gnome.desktop` and
`xsessions/gnome.desktop` so I ommitted adding this to LightDM.

This will simply make the `sessionPath` more likely to work.

This isn't strictly necessary yet as LightDM doesn't read the wayland sessions,
but there's no harm in being explicit.

The test now runs wayland, which means we can no longer use X11 style testing.
Instead we get gnome shell to execute javascript through its dbus interface.