Move the "Enable" checkbox in the date form field before the date input

For screen reader users, the "enable" checkbox comes after the date input and calendar picker. It would be a better experience if the "Enable" checkbox were to be put before the enabled/disabled fields, so that this is read before the rest of the date inputs and the user flow is maintained.

The issue may also occur to users who use a high level of magnification and don't have the whole input group in their viewport.

Steps to reproduce (using a screen reader):

• login as a teacher
• go to a course and add a new page module
• go to the "Activity Completion" section 
• note that the "Enable" option is read after the date
• uncheck the "Enable" checkbox
• navigate the same section again with the disabled date
• note that it is not clear wether the date is enabled
• enable the fields
• note how you must go back to set the date