[TYPO3-core] RFC: #15576: Enable customization for the backend and frontend fatal error messages

[Benjamin Mack]

Hey,

committed Aske's version with two minor modifications (type errors
"RuntimeError" => "RuntimeException") to trunk.

Revisions: #9098 and #9099

Alrighty, next steps:
 - new design to be in style with the new BE design / login screen.
 - possibility to include your own HTML template
 - check with v5 team, what their idea of exceptions are (since we'd
need an exception type with message, code = timestamp and title information)

Thanks a bunch to Denmark!
Benni.