MDL-43960 assign: Add missing include

There was a report of mod_assign_save_grade webservice failing because of this.
I couldn't reproduce it, but grepping the code found one place where this include
should be added.
MDL-44573: Remove HTML tags in outputs column in offline grading worksheet
MDL-43985 Assign: Allow teachers to skip notifying students about grade update.

backport of MDL-33600
MDL-44665 declare all quiz page types in the blocks UI.
Merge branch 'MDL-43960-26' of git://github.com/damyon/moodle into MOODLE_26_STABLE
Merge branch 'MDL-44665_26' of git://github.com/timhunt/moodle into MOODLE_26_STABLE
Merge branch 'mdl44573-moodle26' of git://github.com/tlock/moodle into MOODLE_26_STABLE
Merge branch 'wip-MDL-41285-m26' of git://github.com/marinaglancy/moodle into MOODLE_26_STABLE
Merge branch 'wip-MDL-44686-m26' of git://github.com/marinaglancy/moodle into MOODLE_26_STABLE
MDL-40872 Restore functionality of showrecentsubmissions setting
MDL-40843 behat: allow to specify grouping by idnumber in module generator
MDL-40843 behat: step definitions for recent activity block and report
MDL-40843 recent_activity: corrections to grouping and user fields
MDL-40843 quiz: behat test for recent activity
MDL-40843 feedback: behat test for recent activity
MDL-40843 assign: behat test for recent activity
MDL-40843 forum: behat test for recent activity
MDL-40843 glossary: behat test for recent activity
MDL-40843 workshop: behat test for recent activity
MDL-40843 workshop: show user names in recent activity