DDMsgReader can be called directly as a loadable module
DDMsgReader can now be called directly as a loadable module by Synchronet (though requires the included ddmr_lm.js if DDMsgReader.js is not in sbbs/exec or sbbs/mods). Also, refactored DDMsgReader to use attr_conv.js and removed the attribute conversion functions from this script. Also added a parameter to convertAttrsToSyncPerSysCfg() in attr_conv.js to specify whether or not to convert ANSI codes to Synchronet attribute codes.