Merge pull request #70 from jmontoyaa/1.9.x

Undo images in social buttons see #6015
Updating version.php to version 198
Allow import of csv field username or Username to fit export format
Allow csv import file with get_lang("Username") field to fit export format not english
Unremove 'checkbox', 'unsubscribe_users' (see #6179 for info)
Added 1.9.8 to changelog
Minor update to install script for 1.9.8
Minor - removing whitespaces
Should fix bug BT#6294 when uploading a file the itemproperty.insert_user_id is not correctly saved, we now take the student_publication.user_id to identify the author.