Fixed layout config and aggressive string conversion

There was a few problem I fixed here:

In the function `syslogAin2Appender`, the layout parameter was ignored and I removed it.

Also, adding the `categoryName` at the beginning of the data turns everything into a string. This had the unfortunate effect to 'erase' the stack trace for errors, which are otherwise handled in the `messagePassThroughLayout`.

```javascript
// before
logger.error(new Error('boom'));
// output:
// [2014-03-04 13:54:44.283] [ERROR] [default] - [Error: BOOM]

// now the output is:
[2014-03-04 13:54:44.283] [ERROR] [default] - [Error: BOOM]
Error: BOOM
    at Object.<anonymous> (/home/greg/tests/log4jsTest/index.js:44:14)
    at Module._compile (module.js:456:26)
    at Object.Module._extensions..js (module.js:474:10)
    at Module.load (module.js:356:32)
    at Function.Module._load (module.js:312:12)
    at Function.Module.runMain (module.js:497:10)
    at startup (node.js:119:16)
    at node.js:902:3
```