Bug 13136: Add missing help file for label-manage.pl

Bug 13136: Add missing help file for label-manage.pl

This patch adds in a help file for the new label-manage page.

To test:

* visit label creator
* click manage and choose an option
* click 'help' and confirm the file loads
* repeat for all options under manage

Signed-off-by: Hector Castro <hector.hecaxmmx@gmail.com>
Works as advertised. Tab char corrected

Signed-off-by: Jonathan Druart <jonathan.druart@bugs.koha-community.org>
Signed-off-by: Jesse Weaver <jweaver@bywatersolutions.com>
(cherry picked from commit 8a02409d180d4e4be8a2d9bef6be5373a8b1a907)
Signed-off-by: Julian Maurice <julian.maurice@biblibre.com>