[TASK] Allow line breaks in ext_conf_template description

The description of configuration in the EM should allow
line breaks.

Resolves: #61323
Releases: 6.3
Change-Id: I7a1020e72d6385ba30b933ddde555092f5d2767f
Reviewed-on: http://review.typo3.org/32633
Reviewed-by: Stefan Froemken <froemken@gmail.com>
Tested-by: Stefan Froemken <froemken@gmail.com>
Reviewed-by: Peter Kraume <peter.kraume@gmx.de>
Tested-by: Peter Kraume <peter.kraume@gmx.de>
Reviewed-by: Christian Kuhn <lolli@schwarzbu.ch>
Tested-by: Christian Kuhn <lolli@schwarzbu.ch>
Reviewed-by: Helmut Hummel <helmut.hummel@typo3.org>
Tested-by: Helmut Hummel <helmut.hummel@typo3.org>