Transaction rename and function ordering

This pull request is simplistic in nature.

Other than cleaning up the Bitcoin core test integration syncscript, some small function re-ordering commits, the only real functional change was in the use of an `Array` of `ECPubKeys` instead of `pubKeyBuffers` for `Script.createMultisigScriptPubKey`.

The rename of `Transaction.prototype.hashTransactionForSignature` was changed to `Transaction.prototype.hashForSignature` to remove an implied context in the name.

`Transaction.toBuffer/fromBuffer` is now used instead of `serialize/deserialize`, as this is more consistent with the convention used throughout the project.

This was chosen to make the API simpler, and more consistent with what will (soon) be expected from signatures.
The serialization of these objects should ideally not occur until the last moment where they are actually being serialized for transport.