create a BufferedReader over the specified text file
read the *.dfn file and create the variables for this data set
ready to read the data file after an open() using
either loadDataFile() -- loads entire file into memory
access the data directly using getTextRecord(n), getNumericRecord(n)
or initDataFile() -- does initial pass over file using the buffer
access through the buffer using getNextTextRecord(), getNextNumericRecord()