Delete flag is not NOT editable and NOT shown on add form

expect to fix #6

the delete flag now is not shown on add form. The  implementation might not be ideal and can be improved

btw, I also modified the model.py to make the delete flag not editable.  This is related to #36 since we may need to have two moderators to both agree on changing the flag so making the flag itself not editable and using a delete button to modify it seems to be reasonable.