Alter urea & creatinine units

[finncatling]

In figures and tables, change urea to BUN, and switch creatinine units to mg/dL

[finncatling]

Need to add:

• Conversion function (that takes DataFrame as argument)
• Switch in plot_creatinine_urea_redaction to use conversion function
• Switch in generate_demographic_table to use conversion function
• Switch in PDPFigure (the unit conversion is a linear transformation, so easiest just to change axes & labels for the relevant subplots)

then need to alter PDP terms in scripts 07 and 08, and the PDP filenames in scripts 07, 08, 11 and 13

[finncatling]

Conversion factors:

• Creatinine (mmol/L) / 88.42 = Creatinine (mg/dL)
• Urea (mmol/L) / 0.357 = BUN (mg/dL)

[finncatling]

so easiest just to change axes & labels for the relevant subplots

See Isssue #147 for the problems this creates with matplotlib's tight_layout