Moved batch ID calculation off the IO thread.

components/net/sf/briar/protocol/AckReader.java

components/net/sf/briar/protocol/BatchReader.java

components/net/sf/briar/protocol/MessageReader.java

components/net/sf/briar/protocol/OfferReader.java

components/net/sf/briar/protocol/ProtocolModule.java

components/net/sf/briar/protocol/RequestReader.java

...nents/net/sf/briar/protocol/SubscriptionUpdateReader.java

components/net/sf/briar/protocol/TransportUpdateReader.java

components/net/sf/briar/protocol/UnverifiedBatchFactory.java

...nts/net/sf/briar/protocol/UnverifiedBatchFactoryImpl.java

components/net/sf/briar/protocol/UnverifiedBatchImpl.java

test/build.xml

test/net/sf/briar/protocol/BatchReaderTest.java

test/net/sf/briar/protocol/UnverifiedBatchImplTest.java