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);
```


Would you prefer I just add a note to fix the idle timeout in the JIRA ticket and close the PRs?  A current workaround is to just set both READ_TIMEOUT and WRITE_TIMEOUT so it is not a big deal to wait a bit.