Share parameters parsing code between 'contract invokefunction' and
'vm run' commands. It allows VM CLI to parse more complicated parameter
types including arrays and file-backed bytestrings.
Some commands don't accept arguments, but users try giving them and don't
notice a mistake. It's a bit more user-friendly to tell the user that there is
something wrong with the way he tries to use the command.
We have a lot of common code which is shared between `smartcontract` and
`wallet` cli packages. It's convinient to keep it in a separate helper
package in order to avoid functional cli packages dependencies.
