MDL-45781 quiz autosave: detect and report when the session is lost.

and also other errors.
Automatically generated installer lang files
MDL-35514 mod_forum: Fixed warning message to students in forums with groups
MDL-45763 question Random qtype should use '0' or '1' question text.

Some time ago, it when from using '0' for no-subcategories to blank.
Change to properly define '0' or '1', update old questions, and make
sure to fix newly restored questions.
Merge branch 'MDL-33763-27' of git://github.com/ankitagarwal/moodle into MOODLE_27_STABLE
MDL-45804 mod_workshop: fixed objecttable specified for the submission_reassessed event
Merge branch 'm27_MDL-45726' of https://github.com/danmarsden/moodle into MOODLE_27_STABLE
MDL-45714 backup: Less aggressive removal of old backup dirs

The old 4 hour standard was too aggressive and can cause backup files
to be removed while they were still in use. Now the same as cron,
1 week.
MDL-18162 mod_forum: Correct phpdoc for forum_clean_search_terms
Merge branch 'MDL-45781_27' of git://github.com/timhunt/moodle into MOODLE_27_STABLE
MDL-45634 editor_atto: Adding type button to toolbar buttons

This prevents the browser to assume that those buttons are submit
buttons. In which case the submit action was stolen and the form
could not be submitted pressing the 'enter' key.
MDL-45781 mod_quiz: Shifted files did not match CI version
Merge branch 'm27_MDL-44098' of git://github.com/greg-or/moodle-mod_assign into MOODLE_27_STABLE
Merge branch 'MDL-45677_m27' of https://github.com/markn86/moodle into MOODLE_27_STABLE
Merge branch 'MDL-45592_27' of git://github.com/grabs/moodle into MOODLE_27_STABLE
MDL-42953 Themes: Fixing CSS for headers of central blocks
MDL-44054 quiz_statistics fix lang string concatenation.
Merge branch '45333-27' of git://github.com/samhemelryk/moodle into MOODLE_27_STABLE
Merge branch 'MDL-44620_master' of git://github.com/dmonllao/moodle into MOODLE_27_STABLE
MDL-45789 mod_wiki: removed undefined "$this->other['itemid']" from the comments_viewed event description