Adding 'FundingInfo' abstract class to pair together unsignedTxs and the utxos used to fund them

rename 'unsignedTx' -> 'transaction' in FundingInfo trait

src/main/scala/org/bitcoins/core/protocol/blockchain/BlockHeader.scala

@@ -60,7 +60,8 @@ sealed trait BlockHeader extends NetworkElement {
 
   def merkleRootHash: DoubleSha256Digest
 
-  /** Returns the merkle root hash in BIG ENDIAN format. This is not compatible with the bitcoin
+  /**
+   * Returns the merkle root hash in BIG ENDIAN format. This is not compatible with the bitcoin
    * protocol but it is useful for rpc clients and block explorers
    * See this link for more info
    * [[https://bitcoin.stackexchange.com/questions/2063/why-does-the-bitcoin-protocol-use-the-little-endian-notation]]

src/main/scala/org/bitcoins/core/util/Factory.scala

@@ -21,4 +21,7 @@ trait Factory[T] {
   def apply(hex: String): T = fromHex(hex)
 
   def logger: Logger = BitcoinSLogger.logger
+
+  /** Allows a `def foo[C: Factory]()` construction. */
+  implicit def self: Factory[T] = this
 }

src/main/scala/org/bitcoins/core/wallet/signer/FundingInfo.scala

@@ -0,0 +1,35 @@
+package org.bitcoins.core.wallet.signer
+
+import org.bitcoins.core.protocol.transaction.{ BaseTransaction, Transaction, WitnessTransaction }
+import org.bitcoins.core.wallet.utxo.{ BitcoinUTXOSpendingInfo, UTXOSpendingInfo }
+
+/**
+ * This meant to represent the class used to 'fund' an
+ * unsigned [[Transaction]].
+ * This is useful for when we have multiple [[org.bitcoins.core.config.NetworkParameters]]
+ * that each have their own transaction type. I.e. we should only be able to have
+ * BitcoinTransactions paired with [[BitcoinUTXOSpendingInfo]], the same would apply for litecoin etc.
+ */
+sealed abstract class FundingInfo {
+  /** The transaction we are funding with the utxos */
+  def transaction: Transaction
+  /** The utxos used to fund the tx */
+  def utxos: Seq[UTXOSpendingInfo]
+}
+
+sealed abstract class BitcoinFundingInfo extends FundingInfo {
+  override def utxos: Seq[BitcoinUTXOSpendingInfo]
+}
+
+object BitcoinFundingInfo {
+  private case class BitcoinFundingInfoImpl(
+    transaction: Transaction,
+    utxos: Seq[BitcoinUTXOSpendingInfo]) extends BitcoinFundingInfo
+  def apply(tx: BaseTransaction, utxos: Seq[BitcoinUTXOSpendingInfo]): BitcoinFundingInfo = {
+    BitcoinFundingInfoImpl(tx, utxos)
+  }
+
+  def apply(wtx: WitnessTransaction, utxos: Seq[BitcoinUTXOSpendingInfo]): BitcoinFundingInfo = {
+    BitcoinFundingInfoImpl(wtx, utxos)
+  }
+}