Include tx.hex in unspents

[msmalley]

In most cases, with new BitcoinJS library, you now need to supply the whole TX HEX for non-witness unspents ...

This involves having to do a utxo/transaction on each unspents to get the full tx.hex ...

This could also be added / accessed via an additional parameter?

[AFwcxx]

This feature is added in this commit.

Example of body request:

{
    "address": "<address>",
    "options": {
        "txhex": true // Default: false
    }
}