Implement CompiledTransaction object

[bobbinth]

A CompiledTransaction object is the result of compiling a set of note scripts in the context of an account. This process would be performed by a TransactionCompiler and would look as follows:

Compiled transaction consists of the following components:

Component	Type	Description
Account ID	1 element	Identifier of the account involved in the transaction.
Consumed notes	Vec<Note>	A list of objects for all notes consumed in the transaction (if any).
Tx script root	Digest	MAST root of the tx script for the transaction (if any).
Tx program	Program	An executable program describing the transaction.

Notice that CompiledTransaction object does not actually contain any of the account data (except for Account ID). Thus, we assume that it will be passed to a component which can look up all required account data somewhere before processing the transaction further.