Fix ag_delete_participant

Fixes #505. This fix touches SQL code. ag_delete_participant now does not
remove samples, instead only removing logs and survey data. If samples also
need to be removed, that will have to be done separately.
Modify files that used ag_delete_participant

Added logic to remove samples only in places where it's needed to do so. Also
cleaned up some tabs/spaces heterogeneity in submit_human_survey.psp