add alias for null handler - fixes #133

[gggeek]

Fixes #133

[jderusse]

Could you please add tests?

In YAML I think you can escape the 'null' to fix solve this, but indeed this is an issue with XML configuration.
I wonder if it worth adding a new specific handler while people can also use the noop handle to achieve almost the same thing..

[gggeek]

In YAML I think you can escape the 'null' to fix solve this

True, but it still probably bites many developers the first time that they try to set it up. They might find it easier to use null_handler rather than 'null'

I wonder if it worth adding a new specific handler while people can also use the noop handle to achieve almost the same thing..

I am not sure I get what you mean here... It seems to me that noop handler and null handler behave differently, as the latter is a blackhole sink, while the former is not (truly, making the difference more visible would be welcome). Besides, this is not a new handler, just as easier way to set up an handler which already exists

I'll take a look at tests - but I might need some support with those