[FR] Allow admin to provide skeleton files and folders

## Is your feature request related to a problem? Please describe.
As an admin, I want to provide my users with a folder structure or documents that make it easier to get started with the software.

Also for ownCloud and marketing it is a useful feature if for example whitepapers and test documents can be provided.

## Describe the solution you'd like
In ownCloud 10 it is possible to specify a path with a config parameter where the documents or folder structure is located that will be provided during provisioning.

(https://doc.owncloud.com/server/next/admin_manual/configuration/server/config_sample_php_parameters.html#define-the-directory-where-the-skeleton-files-are-located)

This feature would gain even more value with differentiation of provisioned content based on groups.