NTCP2 code consolidation, minor changes

router/java/src/net/i2p/data/router/RouterAddress.java

router/java/src/net/i2p/router/RouterVersion.java

...src/net/i2p/router/transport/crypto/X25519KeyFactory.java

.../net/i2p/router/transport/ntcp/InboundEstablishState.java

.../java/src/net/i2p/router/transport/ntcp/NTCP2Options.java

...ava/src/net/i2p/router/transport/ntcp/NTCPConnection.java

...java/src/net/i2p/router/transport/ntcp/NTCPTransport.java