Instead returning the time when the chapter was created or modified we
were returning the time when the book was created or modified.

An earlier Behat fix made the use of autocomplete stricter on checking
an exact match instead of a substring, which in turn broke this use
which was searching for a partial match.

Firstly - the list of roles to filter needs to be a combination of the assignable roles and the existing roles in the course.
Secondly - the auto-complete behat step needs to search for entire strings, not substrings.

The form-autocomplete-original-select was applied to the wrong element.

inplaceeditable selects => inplaceeditable autocompletes

Also minor fix to PHPDocs.