Add a custom error message dialog
Let exception handling middleware split error message and detail

Splitting error message from details like tracebacks allows the front-end to
present errors in a cleaner way.
Skeleton splitting/merging: generalize error message
Let submitter use new error dialog
Use error dialog for split/join permission errors
Support ok-on-enter for options dialog's input fields

By default an input field of the options dialog doesn't show this behavior. It
can, however, be activated with an option to the input field creation method.
Submit add-annotation dialog when enter is pressed in an input field

This makes adding annotations more convenient.