Display3: complete overhaul, more flexible and a new login feature

Complete overhaul and update of Display3. The flexibility to tailor the user interface has increased and there is an interesting new feature: Visitors can log in!
When disabled, visitors will not be able to log in and events will be shown according to the settings in the user group of the Public Access user. When enabled, a login button will be shown at the right upper corner. A not (yet) logged in user will see events according to the settings in the user group of the Public Access user. A logged in user will see events according to the settings in his/her user group.
If enabled and the Public Access user has no rights, the display will open directly with the login form. When a user logs in, he will automatically be remembered during the number of days specified on the Settings page of the calendar, under 'User Accounts'.