[FEATURE] Introduce prepend option for Select ViewHelper

A common use case with select fields is to have a 'empty' option at
first position in the options list.

The patch provides the possibility to add a label and additionally
a value, which will be rendered in the option list.

Change-Id: I4fac7372661473d7abbcc209a0fdbd933e65e315
Resolves: #26595
Releases: 6.1
Reviewed-on: https://review.typo3.org/17276
Reviewed-by: Wouter Wolters
Tested-by: Wouter Wolters
Reviewed-by: Thomas Loeffler
Tested-by: Thomas Loeffler
Reviewed-by: Anja Leichsenring
Tested-by: Anja Leichsenring