[FEATURE] IRRE - Possibility to render custom header controls

Render custom header controls by using a render function
defined in TCA field configuration customControls/userFunc

Change-Id: I8a628c9434c540a1cc79156f3bcb4c35b1a3f1c3
Resolves: #34283
Releases: 4.7
Reviewed-on: http://review.typo3.org/9207
Reviewed-by: Ingmar Schlecht
Tested-by: Ingmar Schlecht
Reviewed-by: Steffen Ritter
Reviewed-by: Georg Ringer
Tested-by: Georg Ringer