OO-852: fix warn from logging, add commit every 5 user updates, add link to the creator's visit card of a task

OO-622,CL-225: remove username from GUI in place where is not really needed and students can see it. Mark others place with //TODO username where it need more works and/or the username is only visible by author/coach/admin... Additional fix the setup sql for MySQL (index too long).

OO-530,OO-537: as follow-up of the work in 8.3, remove some maps which are not really useful, remove more unused variables, remove the views and their mapping...

OO-293: better back support in course (run), better switch between sites and dynamic tabs, better behavior after closing a tab (stack of previous tabs/sites not limited to 1 site)

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branch : 80-patch