Improve EthereumListener

[mkalinin]

Currently CompositeEthereumListener invokes all defined listeners on any occurred event which is pretty inefficient. It also impacts on memory consumption.
Possible fix: drive listeners in a pub/sub fashion. It would also nice to have a possibility to define one-off listeners that are detached when a certain event has been caught.

Recap:

• use pub/sub pattern to invoke listener only if it has a subscription to a certain event
• provide a kind of evict() method that removes listener when current invocation is finished
• make listener for one-off events like onSyncDone remove itself in automatic fashion
• get rid of trace() and its usage all over the codebase

Example of listener with evict:

ethereum.addListener(new EthereumListenerAdapter() {
    @Override
    public void onPendingTransactionUpdate(TransactionReceipt txReceipt, PendingTransactionState state, Block block) {
        if (FastByteComparisons.equal(depositTxHash, txReceipt.getTransaction().getHash()) &&
                state == PendingTransactionState.INCLUDED) {
            depositFuture.complete(txReceipt);

            evict();
        }
    }
});