First pass at creating OpenSesame plug-ins
- Tested only with the `dummytracker` and `dumbdummy`
- Mimicks the structure of the `opensesame_eyelink_plugins`
Some minor bugfixes to the `OSMouse` class and the dummy trackers
Merge pull request #9 from smathot/master

Looking good! I'll give 'em a test run as soon as possible (that is: when I can access the labs again, probably in the new year...).