3rd party filters (out of beta, test & feature complete)

[jmshal]

See #4

[jmshal]

If anybody would like to experiment with the basic filter API functionality, that would be awesome. I'm still working on a clever filter to normalise user input from l33t speak to basic english.

[jmshal]

I don't have enough time to finish working on the extension, so this issue is being pushed back to at least 3.0.9 for now. Sorry. If anybody wants to help finish it off, please let me know and I'll add you to the private repo.