Porting the code to 2.7

        * Fix warnings related to context, settype
        * Fix header displayed before redirection
        * Fix upgrade script missing 'return true' at the end
        * editor file support + many various fix on the fly
        * fix assign user page not working
        * add file support to notes in the assign user page
        * add missing lang string for helpdesk permissions
        * Add some default values to the email plain text / title settings so administrator can reset the original value
Backport MOODLE_27_STABLE to MOODLE_22_STABLE

* add back previous/next
* fix the file serving script to support the 2.2 version of send_stored_file()
fix grab redirect url
Update README
Port watcher/hd_user tables + file api support + some previous 2.X improvement - it is a massive mix of many commits from Jon Doane/David Zaharee/Jerome Mouneyrac
Downgrade the required version to the first 2.2
Fix various warnings and errors related to 2.7