Plugins can get called for every message

Also, multiple plugins can have the same action word.

Signed-off-by: Simon Marchi <simon.marchi@polymtl.ca>
Signed-off-by: François Rajotte <francois.rajotte@polymtl.ca>
Add sound plugin

Signed-off-by: François Rajotte <francois.rajotte@polymtl.ca>
Signed-off-by: Simon Marchi <simon.marchi@polymtl.ca>