Updating lang vars.
Fixing PHP warning
Adding new question selection option for exercises.
Fixing question list bugs.
Hiding unused option.
Updating chosen lib.
Removing constant in Security::remove_XSS()
Minor exercise merging with 1.10
Adding hide_question_title option.
Adding hide question title option.
Adding hide question option style.
Sending style for question hide title option.
Minor cosmetic changes
Updating langs.
Updating Chash dbs
Updating lang vars + fixing exercise with the new option (Question select type).
Fixing wrong changed modification.
Updating from 1.10
Fixing correct exercise
Merging with 1.10