Allow timeouts to be set dynamically.

I'm not sure which is correct to use here.
```
connection.getSourceChannel().getOption(Options.READ_TIMEOUT);
```
or
```
connection.getOption(Options.READ_TIMEOUT);
```


Originally this was by design, as the original implementation had a measurable performance impact. This is probably ok now though. 

There is a JIRA to improve all this timeout stuff at https://issues.jboss.org/browse/UNDERTOW-265, but I have not started working on it yet because I am still thinking about exactly what options we require.