Enhancement: Introduce sharing jail

We've added the sharing jail to oCIS which means that navigating and 
working with shares now happens inside the `Shares` navigation item.

https://github.com/owncloud/web/pull/6593
https://github.com/owncloud/web/pull/6909
https://github.com/owncloud/web/pull/6916
https://github.com/owncloud/web/issues/5152
https://github.com/owncloud/web/issues/6448
