Rework Workout creation form to be simpler

[cherking19]

Currently every time the form is updated the information is sent up the widget tree to the root parent widget which contains the master workout object. Instead, each child widget should maintain its own relevant object and the master workout object should be reassembled on create.

[cherking19]

Actually no need to reassemble, just need to pass the workout object from the root widget down the tree. Because it's a reference to the object, changes within child widgets to this reference will update the root object