Enhancement: Personal shares can be shown and hidden

On the shared-with-me page, there is no distinction between pending, accepted and rejected shares anymore.
Instead, the user can toggle to display either shown or hidden shares.

Furthermore, accepting and rejecting shares has been renamed to "enable sync"/"disable sync" to better reflect what's happening on the server and on other devices.

https://github.com/owncloud/web/issues/9531
https://github.com/owncloud/web/pull/9718
https://github.com/owncloud/web/pull/10097
https://github.com/owncloud/web/pull/10321
