Abort experiment on esc press is now handled in libeyelink

 - Esc-presses during drift correct are now dealt with more consistently.
Instead of in eyelink_calibrate or in eyelink_drift correct, this now
takes place in eyelink.drift_correct and eyelink.calibrate, so this behavior
is consistent throughout the experiment.

 - to prevent bloating of eyelink.drift_correct, manual drift correct now has
its own function as well. The documentation of these functions needs to be
further updated still
Merge branch 'clean_esc_press'

Conflicts:
	eyelink_calibrate/libeyelink.py

Last commit was too early -- attempt fix