ClientBootstrap and ServerBootstrap should accept socket options

One can configure socket level options (TCP_NODELAY, etc) in Netty's Bootstrap like this:
```
this.channel = new Bootstrap().group(rpcClient.group).channel(rpcClient.channelClass)
.option(ChannelOption.TCP_NODELAY, rpcClient.isTcpNoDelay())
.option(ChannelOption.SO_KEEPALIVE, rpcClient.tcpKeepAlive)
.option(ChannelOption.CONNECT_TIMEOUT_MILLIS, rpcClient.connectTO)
```
At least in ServerBootstrap there is a configurable ServerSockerFactory which can be used to configure the socket. In ClientBootstrap, I could not find an easy way to do that.

We need this for the HBase-native-client, happening here: https://issues.apache.org/jira/browse/HBASE-14850