Connection readers and writers don't need the connection context.

api/net/sf/briar/api/transport/ConnectionReaderFactory.java

api/net/sf/briar/api/transport/ConnectionWriterFactory.java

...s/net/sf/briar/transport/ConnectionReaderFactoryImpl.java

...s/net/sf/briar/transport/ConnectionWriterFactoryImpl.java

...net/sf/briar/transport/batch/IncomingBatchConnection.java

...net/sf/briar/transport/batch/OutgoingBatchConnection.java

...t/sf/briar/transport/stream/IncomingStreamConnection.java

...t/sf/briar/transport/stream/OutgoingStreamConnection.java

test/net/sf/briar/ProtocolIntegrationTest.java

test/net/sf/briar/transport/ConnectionWriterTest.java