Move help from gnome-user-docs

Also add licenses to all files.

Signed-off-by: Michael Hill <mdhill@gnome.org>
Signed-off-by: Baptiste Mille-Mathias <baptiste.millemathias@gmail.com>
Signed-off-by: Andika Triwidada <andika@gmail.com>
Signed-off-by: Julita Inca <jinca@gnome.org>
Signed-off-by: Marta Maria Casetti <mmcasetti@gmail.com>
Fix links in help