Add easy execution of a newly edited exercise

[oz1cz]

Add a button to test a newly edited exercise on the exercise editing page. (You can, for example, add a "not scoring" parameter to the execution of an exercise and use that parameter to modify the text on the buttons that terminate the execution. This can also be used to modify the same buttons when an exercise is executed by a person who is not logged in.)

[tmccormack165]

This issue is now resolved. There is now a button called "Test Exercise" that will allow a teacher to test an exercise while they are creating it.

After "Test Exercise" is pressed the exercise is displayed with the most recent parameters:

Users can press "Back" to continue editing the exercise.