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-41285 block_recent_activity: behat test for structural changes
MDL-44686 behat: limit failure filename length to 255 chars
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
Automatically generated installer lang files
Merge branch 'install_26_STABLE' of git://git.moodle.org/moodle-install into MOODLE_26_STABLE
weekly release 2.6.2+
MDL-41063 Lesson qformat_default class is missing an error function