Allow separate mount of data directory

[thatRailsGuy]

"Data Directory" is a loaded term.

In the Nextcloud container, the ansible-nas nextcloud_data_directory is mounted at /var/www/html. Inside that folder is another folder called data that could be useful to define to a different storage. This requires adding another volume mount to /var/www/html/data with a variable to support it. We could default it to mount inside the default ansible-nas docker data location but I find it useful to store it on my samba shares drive.

[thatRailsGuy]

I could make a pull request if this is agreeable.

[khartahk]

I think this PR #497 would address this issue. I'm using a separate data directory so that it's not in the root folder from where nextcloud is served from. I haven't completely finish the changes yet but would love any comments / inputs or thoughts regarding the changes.