Option to only show windows in this workspace in dock

[kdwk]

Problem

Currently, dock puts an open indicator under any app that is open in any workspace. However, there is no indication of which workspace the windows are opened in, and no option to only show windows in the current workspace

Proposal

Add an option in the Pantheon shell switchboard plug (dock section) to to allow users to toggle 'Only show windows in current workspace'

Prior Art

This is how the Dash to Dock Gnome extension does it. However, 'isolate workspaces' may be a little vague in my opinion.

[danirabbit]

Seems like a duplicate of #134. Closing as duplicate