Fixup File security metadata reporting for Unix

* Add functional tests for file permission reporting
* Always report file modes as a string. Otherwise UIs will have to know to print mode integers using octal.
* Remove ad-hod implementation of file permission reporting, replace with ScanAccessControl (this was intended to be the original implementation but a second one was added because of confusion over requirements).
* Refactor how resource security attributes are added to file and file-like resources in order to make unit testing possible (provided in a future patch).

Still todo: Add windows implementation of file security reporting.