Add Occam factor calculation

Add a function to estimate the Occam factor for a given fit.

Is this different from the prior volume?

Maybe (depending on your definition). For 1D it's the posterior standard deviation say, over the prior width.

added Feature-request label

mentioned in merge request !86 (merged)

closed via merge request !86 (merged)

closed via commit e990bc56

mentioned in commit e990bc56

unassigned @gregory.ashton