MDL-40074 refactoring of quiz code

to reuse code fro quiz attempt walk through
MDL-40074 quiz attempt walk through test
Automatically generated installer lang files
Automatically generated installer lang files
MDL-35851 lesson: Handle importing questions into an empty lesson.

Also - make sure the page we are updating belongs to the lesson.
Merge branch 'wip_MDL-40074' of https://github.com/jamiepratt/moodle
Merge branch 'install_master' of git://git.moodle.cz/moodle-install
weekly release 2.6dev
MDL-28019 Added plugin repository_areafiles
MDL-28019 repository_areafiles is added to the standard plugins list
MDL-28019 Added plugin tinymce_managefiles
MDL-28019 tinymce_managefiles is added to the standard plugins list
MDL-28019 Added setType in the moodleform
MDL-28019 Unescaping the file name
MDL-28019 Remove obsolete comment
MDL-28019 Support for possible subdirs in textarea

Subdirs are usually disabled for textareas in moodle but it was reported that they can be present after upgrade
MDL-28019 Support for possible subdirs in repository_areafiles