Fix 500 when saving /site/edit without email
When saving /site/edit with no no_reply_email set, a 500 error page
would be returned due to an empty value being passed as value to
the datastore (which is not allowed for email fields).
Remove __melange_queries logging
It causes the local instance to become very slow, as it has to pickle
all queries. A better solution would be to store them in the per
request value store and then add middleware to store that data at
end-of-request.