Update : Created reset survey method

Reset survey [ Delete all responded answers ]
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Destroy survey submission record with respective survey id(survey_id).  Then associated tables data ( survey_mrq_answers and survey_essay_answers) will be automatically destroyed with respective submission id ( survey_submission_id ) as it is dependent => destroy 

Advantage:
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If lecturer wants to reset survey he/she is able to reset and empty all responded answers
Issue raised here [ https://github.com/Coursemology/coursemology.org/issues/140 ]