support pass extra headers while handshaking

[wsky]

used for auth or more

• [x] pass headers while handshake
• [x] validate headers while onConnect
• [x] endpoint can do auth while onConnect
• [x] spring-support can set defaulServerChannelHandler

[wsky]

use onConnect to auth remoting connection, but it was not like remotingSink for rpc-call, it was extra setting for low-level remoting channel.

so i wont add it to remotingSink design, just as a ServerChannelHandler extension

RemotingConfiguration.configure().defaultServerChannelHandler(customHandler);

client maybe like this too.

handshake-auth is special way for websocket channel