When a table is marked as being categorizable, the
categories field is added with an "exclude" flag
hard-coded to 0. Thus it is not possible to hide
this field for editors.

This patch changes the default value to 1 and makes
overridable.

Resolves: #53454
Documentation: #55718
Releases: 6.2
Change-Id: Iff2431b4294b8d3b9cf3dff291186e1a6a2ebafb
Reviewed-on: https://review.typo3.org/27373
Reviewed-by: Wouter Wolters
Tested-by: Wouter Wolters
Reviewed-by: Markus Klein
Tested-by: Markus Klein
Reviewed-by: Francois Suter
Tested-by: Francois Suter