Renamed the reverseOrder configuration setting to reverseListOrder.  Added the enter key as a key to advance to the next message in reader mode.  Added the -subBoard command-line option, which can be used to specify a sub-board to read (by internal code or by number).  Fixed the msgReaderPath variable in DDScanMsgs.js and DDScanSubs.js to contain ../xtrn/DDMsgReader.  Updated the readme to reflect the change in the reverseListOrder configuration setting name, and also re-arranged the installation section of the readme.