Use the standard pre-upgrade datasource names.

Jay's previous commit updated the datasource names to $client's Oracle-modified version of AjaxRating, which was only useful specifically to them. The "standard" old datasource names are what everyone will be using.
Shebang path to perl should be hardcoded.
Correctly call _send_error and _send_json_response.
Minor code cleanup: tabs to spaces, removed extra space at end of lines.
mt-getvotes.cgi updates: documentation, JSON response support, error-checking, and clean-up.
AddVote: use $app->query or fallback to $app->param.
Version bump to 1.4.5.