Added new lean config option com.openexchange.spamhandler.enabled that allows to enable/disable the configured spam handler on a user/contextset/server level.

If no configuration is available the previously configured user setting mail permission bit will be taken into account. If there is a configuration for com.openexchange.spamhandler.enabled available these will be used for the defined scope.

Caution: if the property has once been set via ConfigCascade only these source will be used. You can change it for instance on a user base as described here: http://oxpedia.org/wiki/index.php?title=ConfigCascade . Changing the user configuration afterwards via /opt/open-xchange/sbin/changeuser ... --gui_spam_filter_capabilities_enabled true/false will have no effect!

This option is reloadable.