Adds coverage_model.utils.express_slice
Adds coverage_model.utils.express_slice

utils.express_slice replaces any None components of a slice_ with real values

For example - given a total domain of (20,10):
(slice(None,None,10),slice(3,None,None)) ==> (slice(0,20,10),slice(3,10,1))

ooici/coverage-model,ooici/coverage-model