Make BlockNumber in CLI generic as well

[bkchr]

For some use cases in the CLI we require the BlockNumber, currently we assume the block number fits into u32. This is not correct and thus, we should make the CLI generic over the BlockNumber as well.

#2602

[niklasad1]

@bkchr

Do you mean that for example these should take a type parameter instead in u32?

It doesn't seem possible to do with structopt, see TeXitoi/structopt#128

[bkchr]

Yeah we should remove the u32. We could create your own type struct BlockNumber(String) that we use as parameter to structopt. Parse or whatever structopt uses would make sure that the given parameter is really a number and not a string. In Substrate itself we just put a bound on the "real" BlockNumber type that it needs to implement From<String> or something similar. I think that should work.