Support checking module and scope names

[wsnyder]

Verilator's test driver has a separate check that the hierarchy of signals remains the same, because that feature was not in vcddiff.

https://github.com/verilator/verilator/blob/5b410e9331b1543889287a965d0ea016d9a6b6d7/test_regress/driver.py#L2377

It would be good to support that in vcddiff and then remove related code from Verilator. It's ok if Verilator looses the ability to vheck VCDs if vcddiff is not installed.