Refactor workspace hierarchy

Relocate workspace management in workspace component, overview in workspace-overview, workspaces dialog triggering in its own component and move workspace list into workspaces folder.

This allows to simply a lot of code that is now only trigerred when it should be (e.g. selectors for the workspace or the sidebar only when on a workspace). Also now we can use the router to leave a workspace directly.

This is in preparation for angular 4.2 which is stricter with routing.