Add dependencies for the spectra player.

Signed-off-by: Jean-Yves Tinevez <jeanyves.tinevez@gmail.com>
Empty /plugins.config

Signed-off-by: Jean-Yves Tinevez <jeanyves.tinevez@gmail.com>
WIP: Optofluidics spectra player plugin.

Right now it does the very cumbursome input checks, load the spectra,
and listen to frame change to find the associated spectrum.
TODO: display the associated spectrum.
Signed-off-by: Jean-Yves Tinevez <jeanyves.tinevez@gmail.com>