MDL-47183: viewhiddenactivities should use the module context

Thanks to Paulo Matos for the forum part of this change.
MDL-47585 stats: fixed incorrect user dropdown
Automatically generated installer lang files
Merge branch 'wip-MDL-47585-m27' of git://github.com/marinaglancy/moodle into MOODLE_27_STABLE
MDL-47914 report_stats: better handling of user and mode
Merge branch 'MDL-47183-27' of git://github.com/andrewnicols/moodle into MOODLE_27_STABLE
MDL-47183 post-integration fixes

* Fixed typo with context_module::instance
* Fixed use of $mod->get_context()
Merge branch '47914-27' of git://github.com/samhemelryk/moodle into MOODLE_27_STABLE
Merge branch 'install_27_STABLE' of https://git.in.moodle.com/amosbot/moodle-install into MOODLE_27_STABLE
weekly release 2.7.2+