Enhancement: Make some UI elements/actions optional

Make renaming a share, permanently deleting files and showing the custom permissions role optional via capabilities.
By default, all of these options are enabled/showed.

Capabilities:
* capabilities.files_sharing.can_rename
* capabilities.files.permanent_deletion
* capabilities.files_sharing.allow_custom

https://github.com/owncloud/web/pull/6618
https://github.com/owncloud/web/issues/6324
