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
I'm not sure if we need another endpoint for submitting an experiment based on whether it has started.  It seems to me that fact could be easily derived in the existing endpoint for editing experiments and adding in a conditional statement - checking whether the tracks have been finalized or not, I believe - would suffice.  The method could be broken up into helper methods for each case if your concern is the length, but there is a bit of overlap as is so I'd be comfortable with the added logic.