Moved writers into their own package, replaced public static fields in

api/net/sf/briar/api/db/DatabaseComponent.java

api/net/sf/briar/api/protocol/writers/AckWriter.java

api/net/sf/briar/api/protocol/writers/BatchWriter.java

...et/sf/briar/api/protocol/writers/PacketWriterFactory.java

...net/sf/briar/api/protocol/writers/SubscriptionWriter.java

api/net/sf/briar/api/protocol/writers/TransportWriter.java

api/net/sf/briar/api/serial/Writer.java

components/net/sf/briar/crypto/CryptoModule.java

...nents/net/sf/briar/db/ReadWriteLockDatabaseComponent.java

...onents/net/sf/briar/db/SynchronizedDatabaseComponent.java

components/net/sf/briar/protocol/writers/AckWriterImpl.java

...onents/net/sf/briar/protocol/writers/BatchWriterImpl.java

...et/sf/briar/protocol/writers/PacketWriterFactoryImpl.java

components/net/sf/briar/protocol/writers/WritersModule.java

test/net/sf/briar/db/DatabaseComponentTest.java

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

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

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

...t/sf/briar/protocol/SigningDigestingOutputStreamTest.java