Feature/started experiment editing

Updates the edit experiment form to have a third mode for started experiments. In this mode, you can view all the details of the experiment, but can only update the name and notes.

Also applies updates to experiment tests in line with these and earlier changes.

Remake of #90 against develop
oh, ok my bad.  so, I suppose then that in the test below for ` test_submit_edit_started_experiment_wrong_course` the experiment should have finalized tracks.  given the test case, it wouldn't affect the outcome but it would be more consistent I suppose.