JsonWizard: Remove scratchfile wizard

Replace it with a json wizard based implementation.

Todo: This removes the keyboard shortcut available to trigger
this wizard. We should make sure all wizards are available
for binding keyboard shortcuts to them instead.

Change-Id: I1aa76222d08371e79c40b52aeb26705f3ccb4899
Reviewed-by: Daniel Teske <daniel.teske@digia.com>
Reviewed-by: Tobias Hunger <tobias.hunger@digia.com>