MailGW.handle_message(): as config is used many times in this method, have a local variable instead of going through self.instance.config each time; change config attribute access to container (item) access; where possible, avoid duplicate computing of config settings; fix MAILGW_KEEP_QUOTED_TEXT and MAILGW_LEAVE_BODY_UNCHANGED - config values are boolean now; trim trailing spaces, fix vim modeline

<!-- query.item -->
<span tal:content="structure context/renderQueryForm" />