Keypresses used in iCoder

1: change response to left
2: change response to off
3: change response to right

4: change response to away (if implemented)

5: change response to center
6: toggle trial status on/off
+: increment trial number by 1
-: decrement trial number by 1
enter: adds an entry for the current frame (behavior contingent on trial status)

when one or more log entries is selected:
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delete/backspace: delete selected log entries
+: increment trial number for selected log entries
-: decrement trial number for selected log entries

space: toggle play/pause of video
left arrow: move one frame backward
right arrow: move one frame forward
[: move STEP frames backward
]: move STEP frames forward
