modify api doc for logs

This PR modifies the api doc for logging mechanism
In fact, it is not only `Aria.debug` which determines whether a messaged is logged or not. And changing `Aria.debug` after the framework has started does not change the logging level.
It all depends on the configuration of `aria.core.Log`, which, indeed, contains by default:
```js
this.setLoggingLevel("*", Aria.debug ? this.LEVEL_DEBUG : this.LEVEL_ERROR);
```
So rather than saying only when "Aria.debug is equal to true", I would say: "depending on the configuration of aria.core.Log".