[feature-request] Add ability to show and edit POSIX ACLs & extended user attributes

Many people using Elementary is working with ACL & user_xattr on daily basis.
Currently they should use `getfacl`/`setfacl` in terminal or GUI tool named `Eiciel`, which interrupts their session in `Files` making user experience quite fragmented.

IMO, it would be useful to provide some additional controls for the `Permissions` tab to manage ACLs & user_xattr's.
Perhaps not every Elementary OS user needs to manage ACLs & user_xattr's, so this controls could be somehow made configurable to show/hide.
For design example there are already named `Eiciel`: [https://rofi.roger-ferrer.org/eiciel/screenshots/](https://rofi.roger-ferrer.org/eiciel/screenshots/).

---
Want to back this issue? **[Post a bounty on it!](https://www.bountysource.com/issues/58119203-feature-request-add-ability-to-show-and-edit-posix-acls-extended-user-attributes?utm_campaign=plugin&utm_content=tracker%2F65602118&utm_medium=issues&utm_source=github)** We accept bounties via [Bountysource](https://www.bountysource.com/?utm_campaign=plugin&utm_content=tracker%2F65602118&utm_medium=issues&utm_source=github).