Updating surveys has been broken on wwwadmin

the is_7_to_13 field was removed from the database and from the web form, but
it was explicitly being examined in order to check whether or not the form
had been submited already, resulting in unsuccessful survey updates.
Change juvenile_age from text box to select
Found the buildSelect function, used that instead
Merge pull request #485 from adamrp/fix_wwwadmin_update_survey

Fix wwwadmin update survey