[mapplauncherd] Remove obsolete tests.

The tests in here have been in a completely non-working state for a very long
time, and it's now getting to a point where it hurts, rather than hinders
development. Nuke them from the tree.

In the future, the useful parts can be brought back easily from history.
WIP: [mapplauncherd] Remove X11 dependency from single-instance.

Instead of using windowsystem-specific functionality, ask the system compositor
to activate the given binary for us.