Enhancement: OcTableFiles dropdown menu

The OcTableFiles component now has a slot that will be displayed inside an OcDrop upon 
either right-clicking a table row or the three-dot button on the right end of the row.

https://github.com/owncloud/owncloud-design-system/pull/1420
https://github.com/owncloud/web/issues/5102
https://github.com/owncloud/web/issues/5103
