Feature : add customer licence option

[Thatoo]

It could be nice to be able to use customer licence.
Ask for it at install and also be able to add (and change if needed) in config panel app

Instead of
ynh_install_extra_app_dependencies --repo="deb https://collaboraoffice.com/repos/CollaboraOnline/CODE-debian${DEBIAN_VERSION_NUMBER} ./ " --package="$pkg_dependencies" --key="https://keyserver.ubuntu.com/pks/lookup?op=get&search=0x0C54D189F4BA284D" 2>/dev/null

it would be

ynh_install_extra_app_dependencies --repo="deb https://collaboraoffice.com/repos/CollaboraOnline/${DEBIAN_VERSION_NUMBER}/customer-deb-${CUSTOMER_LICENCE} ./ " --package="$pkg_dependencies" --key="https://keyserver.ubuntu.com/pks/lookup?op=get&search=0x0C54D189F4BA284D" 2>/dev/null

Well, it would also require to change in _common.sh script

pkg_dependencies="coolwsd code-brand hunspell-de-de hunspell-en-gb hunspell-fr hunspell"

to

pkg_dependencies="coolwsd collabora-online-brand hunspell-de-de hunspell-en-gb hunspell-fr hunspell"

I don't know if it is a good idea finally. I drop the idea here anyway.