Several changes which allow first stage of bias studies to be fully run

Can now run and plot output of bias studies (only so far tested on the lowest order functions but in principle higher order functions and different correction schemes are allowed):

1) Submit jobs to lxbatch with code/scripts/sub_bias.py using dat file code/dat/batch_config.dat (designed for 1nh, 8nh or 1nd queues)
2) Extract the results (specifically to construct the envelope given various correction criteria etc. using code/scripts/extract_bias.py and the same dat file as above. This can take a while so can also split this into a series of very small jobs (designed for 8nm queue)
3) Plot the outcome (and save the bias, coverage as a function of POI in root file) using scripts/plot_bias.py and dat file code/dat/plot_config.dat