Converted the outgoing encryption layer from frames to segments.

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

components/net/sf/briar/transport/ConnectionWriterImpl.java

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

.../sf/briar/transport/IncomingSegmentedEncryptionLayer.java

.../sf/briar/transport/NullOutgoingErrorCorrectionLayer.java

...nents/net/sf/briar/transport/OutgoingEncryptionLayer.java

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

.../net/sf/briar/transport/OutgoingErrorCorrectionLayer.java

.../sf/briar/transport/OutgoingSegmentedEncryptionLayer.java

components/net/sf/briar/transport/TagEncoder.java

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

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

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

...t/sf/briar/transport/OutgoingEncryptionLayerImplTest.java

...briar/transport/OutgoingSegmentedEncryptionLayerTest.java