Fixed bugs in parse_numeric and read_plate_setup

example_master_script appears to work: can read the "raw" data and the
plate_legend, and merge the two.

Next step: calibrate
cal_curve.R seems to work

Takes a data frame of raw-but-parsed-and-reshaped data, returns a
similar data frame with columns for calibrated data
cal_curve can output matrix of slopes
Added dialog box to read_biotek
Set up automatic labeling of columns if none specified