Clean up eyelink_log and fix throttle issue with auto-logging
Merge remote-tracking branch 'wkbouter/master' into tmp
Some fixes to the abort-on-escape mechanism
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