Git commits in Moodle 3.0.6 by Michael Aherne

commit 4063900e2bcd395c324ca54163205e25e0a02bb9
Author: Michael Aherne <michael.aherne@strath.ac.uk>
Date:   Fri, 08 Jul 2016 17:48:00 +0800
Tag:    v3.0.6

MDL-55161 assign: Check for existence of gradebook feedback plugin