Clean up HandleConnection
Clean up HandleConnection

* Removes the "smallest read" feature, which resulted in a lot of 1-byte
reads and unnecessary Check calls.
* Make the conditions when checking a protocol cleaner with a switch.
* Rename ProtocolHandler to Protocol, as the name was annoyingly long.
There is an alias interface in place for compatibility for now.
* Rename HandleConnection to HandleConn, as the name was too long.

jmptrader/serve2,Joushou/serve2