New features for Admin page

+ Added functionality to 'edit' and 'remove' buttons on admin "All Food Resources" page.
+ Front-end drop-downs for timeslots update correctly when 
     + editing an existing food resource.
     + an invalid timeslot is given and the form is submitted. 
+ Front-end drop-down for food resource type updates correctly when
     + editing an existing food resource.
     + an invalid timeslot is given and the form is submitted. 
+ Removed food resource enum functionality (obsolete now).