Sprint 2 (User Story #57) - As an admin, I want to disable the option for students to cancel a booking

	Given I am an admin, when I tick the checkbox to either say YES or NO to 'Allow Students to cancel 
	bookings', it will assign the "Days prior to bookings" a 5 or 0 respectively.

	Changes made:

	In the 'view' for the settings file I added a check box that either allows or dis-allows students to
	cancel their booking. Yes and No both have their individual values.
	In the 'view' for the make_booking file, the view_experiment; I added a a new if statement that takes
	the new value that was assigned from the check box to cancel or not to cancel the booking. The other way
	to not allow bookings to be cancelled was already implemented which was "Days prior". So a new message
	would be shown when the booking is not allowed to be cancelled.
	

	How to implement it:
	
	1. Create a Student
	2. Create an experiment
	3. Assign him/her to the experiment
	4. Allocate the calander dates
	5. Go to the settings page tick NO to disallow students to cancel bookings.
	6. When a student goes back to the experiment and tries to cancel the booking, it is faded out and 
		a message appears "You are not allowed to cancel a booking."