Survey: add PDF export of answerable survey
@AliaMori.com suggests we add a PDF/txt export of the surveys to allow for offline survey taking so that we can 1). Distribute draft versions for review by non-Chamilo users and 2). Distribute the same survey for filling out to those who do not have access to the internet.
This would probably require an additional "Add anonymous answers" mode to the survey to be able to input the answers of offline surveys.