Include RCD/Sig in pending transactions

[WhoSoup]

Thanks to @ilzheev for reporting this one.

Regular transactions contain the RCD/Signature for all inputs but pending transactions currently don't. They're not returned by the API so this will need modification to factomd as well.

Todo:

• Expand factomd to include the RCD/Signatures for the inputs in "pending-transactions" call
• Expand lib to use SignedTransactionAddress instead of TransactionAddress for inputs