major enhancements in templates

1) completely rewritten the routine building XML
2) deleted each _sid field
3) moved the field "template" from survey_item to survey

now the philosophy is:
-> a master template is supposed to come from the wise of the centuries so its children (survey generated by it) ARE NOT MODIFICABLE AT ALL
-> survey generated by a master template do ALWAYS support multilanguage
-> if you try to modify a survey generated by a master template a "who touches die" message is displayed
-> if the user continue in spite of the "who touches die" message, the multilang support is dropped and the survey become as generated manually or from a user template
-> if you want to make your own experimentations with survey, you can do (and share) whatever you like BUT using user templates and not multilang master templates