Occurrence filters page is out of date

[cjgrady]

Describe the bug

https://specifysystems.github.io/lmpy/tutorial/occurrence_filters.html is out of date. It was written before the data wrangler concept was fleshed out.

Update it with accurate instructions for using occurrence data wranglers and it would be useful to add the factory method (which may be almost directly copied from https://github.com/specifysystems/lmpy/blob/main/lmpy/data_wrangling/occurrence/README.md)