The transient state can be used to test out changes before committing
them to the proc state. The transient state is currently being used by
the gui to support proper nonce updating without having to wait for a
block. This used to be done by a cached state mechanism which can now
safely by removed.
The Ethereum structure now complies to a EthManager interface which is
being used by the tx pool, block manager and block chain in order to
gain access to each other. It's become simpeler.
TODO: BlockManager => StateManager