allow to omit Value and To for a new transaction

[splix]

Just:

emerald transaction   [--chain=<chain>] <from> <to> [--gas=<gas>] [--gas-price=<price>] [--data=<data>] (--nonce=<nonce> | --upstream=<upstream>)
emerald transaction   [--chain=<chain>] <from> [--gas=<gas>] [--gas-price=<price>] [--data=<data>] (--nonce=<nonce> | --upstream=<upstream>)

Use 0 if not passed. It's especially important for to parameter, because when a use wants to deploy a contract with current schema it need to figure out that zero-address (i.e. count all zeroes), it's error prone.

Also, it's better to make both parameters as named by default but keep full from-to-value as a shorthand:

emerald transaction   [--chain=<chain>] <from> [--to=<address>] [--value=<value>] [--gas=<gas>] [--gas-price=<price>] [--data=<data>] (--nonce=<nonce> | --upstream=<upstream>)
emerald transaction   [--chain=<chain>] <from> <to> <value> [--gas=<gas>] [--gas-price=<price>] [--data=<data>] (--nonce=<nonce> | --upstream=<upstream>)