Adding a "Discard" button when creating a new protocol

[gba-online]

Currently, when creating a new protocol, you can only press Save but not Cancel or Discard. This means that you can only cancel if you close the tab, for example. The disadvantage is that the empty log of the protocol is still saved and you will receive reminders by mail that you have unpublished protocols. But the link in these mails gives a 403 error.

You can only delete this empty protocols by creating a new protocol, then clicking on the "Restore" button that appears in a red box above. Then press "Save", then "Edit" and then "Delete".

[frcroth]

Related to #765