Add Shares breadcrumb root when navigating into a share

[kulmann]

Following UX bug concerns the share jail / ocis

Steps to reproduce

1. As admin, share folder "test" with einstein
2. As einstein, navigate to "Shares", which initially redirects to "Shared with me"
3. As einstein, accept the share and navigate into it

Expected behaviour

The breadcrumbs reflect the page hierarchy and offer a clear path back to where I came from, i.e. a root element "Shares" (the nav item that I clicked) followed by a child element "Shared with me" and then the name of the share that I navigated into.

Actual behaviour

The breadcrumbs show "Shared with me" as root element followed by the name of the share that I navigated into.