relative quantification with delta Cq and delta delta Cq

Upgraded features for relative quantification, new vignettes to explain these, and gave functions more helpful names such as calculate... as well as create...

• lay out and display 96/384-well plates for easy experimental setup (label_plate_rowcol, create_blank_plate, ...)
• read-in Cq and raw data from Roche LightCycler machines with single-channel fluorescence (read_lightcycler_1colour_cq, read_lightcycler_1colour_raw)
• delta Cq: normalization/ relative quantification of Cq data to one or more reference targets by delta count method (calculate_normcq, calculate_deltacq_bysampleid)
• delta delta Cq: normalization of delta Cq data across multiple samples (calculate_deltadeltacq_bytargetid)
• calibration of primer sets including estimating efficiencies and visualization of curves (calculate_efficiency, and see vignettes)
• visualization of amplification and melt curves (calculate_drdt_plate, and see vignettes)