added continuous mode support fix #3

If a command returns SHELLMATTA_CONTINUE all received data is passed to this command until it returns != SHELLMATTA_CONTINUE or a cancel is received
The data is passed stdin like and can be read byte by byte vie shellmatta_read
The stdin buffer is overwritten witch each new char

api/shellmatta.h

@@ -144,6 +144,7 @@ typedef struct
     shellmatta_write_t  write;              /**< pointer to write function              */
     shellmatta_cmd_t    helpCmd;            /**< help command structure                 */
     shellmatta_cmd_t    *cmdList;           /**< pointer to the first command           */
+    shellmatta_cmd_t    *continuousCmd;     /**< command to be called continuously      */
     bool                cmdListIsConst;     /**< true if the #cmdList was passed during
                                                  initialization                         */
     shellmatta_opt_t    optionParser;       /**< option parser sructure                 */