add lock_height to Transaction and TxKernel (#167)

* add lock_height to Transaction and TxKernel, sign msg including both fee and lock_height in kernel
* make the order of the fields in tx and kernel more consistent
* rename to kernel_sig_msg
* add test to cover adding timelocked tx to pool, where tx is invalid based on current height of the blockchain
* add tests for adding timelocked txs to blocks (valid and otherwise)

api/src/endpoints.rs

@@ -76,6 +76,7 @@ impl ApiEndpoint for OutputApi {
 		let commit = Commitment::from_vec(c);
 
 		let out = self.chain.get_unspent(&commit).map_err(|_| Error::NotFound)?;
+
 		let header = self.chain
 			.get_block_header_by_output_commit(&commit)
 			.map_err(|_| Error::NotFound)?;

api/src/types.rs

@@ -50,7 +50,7 @@ pub struct Output {
 	pub proof: pedersen::RangeProof,
 	/// The height of the block creating this output
 	pub height: u64,
-	/// The lock height (spendable after block)
+	/// The lock height (earliest block this output can be spent)
 	pub lock_height: u64,
 }
 
@@ -65,6 +65,7 @@ impl Output {
 			}
 			_ => (OutputType::Transaction, 0),
 		};
+
 		Output {
 			output_type: output_type,
 			commit: output.commit,