Move docs from Uncategorized to Sysasdmin docs

docs/system-admin-documentation/advanced-features/index.rst

...cumentation/advanced-features/multi-data-set-archiving.md

...dmin-documentation/advanced-features/sharing-databases.md

...er-group-management-for-multi-groups-openbis-instances.md

docs/uncategorized/index.rst

...documentation/general-users/additional-functionalities.md