Bugfix: Add and remove to/from favorites

We've fixed bugs related to adding and removing files to/from favorites:
- "favorite" star button in the right sidebar of the files app was not being updated when the favorite-state was modified through a click on the star icon
- toggling the favorites state of the current folder was broken (via both context menu on current folder and right sidebar without a file selection)

https://github.com/owncloud/web/issues/6328
https://github.com/owncloud/web/pull/6330
