Improve substrate target configuration

[xermicus]

Currently there are --address-length and --value-length compile flags to allow metadata generation for differently configured Substrate runtimes. But there is no way to tell the path for the type.

As a UI bonus we could offer some default configurations (e.g. something along the lines --target substrate/default_env or substrate/moonbeam), to offer valid settings for common runtime configurations.

[extraymond]

--address-length is included in the pr #989 by using ns::address_length, maybe need a test for it.

[xermicus]

Solved by: #1084

[xermicus]

As we found out, there also needs to be configuration for Hash length, similar to --address-length, which defaults to 32.