Fix/cancel changes

This is a fix to feature/cancel_changes in order to pass third QA test (i.e. an admin user navigating to the edit intervention page from Canvas modules should return back to Canvas modules upon hitting cancel)

Design explanation: by creating a new edit intervention page specific to modules, this prepares us to down the line add functionality (special preview features if viewing from modules) and change functionality (if editing intervention points directly from modules is no longer desirable)