Merge pull request #143 from apoloval/fix/OrderSubmissionForm

Fix a bug in required fiat amount computation in `Order`
Retrieve connection status directly from the CoinffeinePeerActor
Simplify wallet actor initialization
Renaming BlockchainActorReference -> BlockchainActorRef

For consistency with WalletActorRef. Also add missing tests about this
message.
Make BitcoinPeerActor honor RetrieveWalletActor message
Make CoinffeinePeerActor use RetrieveWalletActor

The point is not relying on the connection process to get the wallet
actor reference. Also fix a heisenbug related to calling
context.become within a future.
Remove the wallet actor ref from BitcoinPeerActor.Started

And deprecate bitcoin connection related messages
Convert BitcoinPeerActor to the join/leave style

Instead of receiving connect/disconnect commands with their 
confirmations, the actor is requested to try joining until succeeding
or to leave the network.
Merge pull request #144 from sortega/task/156_join_leave

Convert BitcoinPeerActor into the join/leave style
Remove unnecessary wrapping class
Use partial functions for MessageGateway subscriptions
Support multiple subscriptions per actor on MessageGateway
Rename Filter -> ReceiveFilter
Support subscription to broker messages
Support SubscribeToBroker on GatewayProbe
Introduce ForwardMessageToBroker

From now on, actors will be able to send messages to the broker
without previous knowledge of its peer id.
Add support for ForwardMessageToBroker to GatewayProbe

Test it by using it on MarketInfoActor (that gets simplified)
Merge pull request #146 from sortega/task/156_join_leave

Extend the MessageGateway interface
Implement a `ServiceActor` trait to have a service-like actor lifecycle

This trait may be used to implement actors that behave as services. I.e., they
can be synchronously started and stopped by receiving service control messages.
Merge pull request #147 from apoloval/task/StartStopService

Implement a `ServiceActor` trait to have a service-like actor lifecycle