WFAU module has no way of identifying deprecated WFCAM images

The WFCAM Science Archive has the concept of deprecated WFCAM images (see e.g. the description of deprecated column here http://wsa.roe.ac.uk/www/gloss_d.html). However the [WFAU](https://github.com/astropy/astroquery/blob/88dd76ddf3c41b66cb62f9ec9712921202190f37/astroquery/wfau/core.py#L24) module doesn't seem to have the option of only downloading undeprecated images?
[Here](https://github.com/astropy/astroquery/blob/88dd76ddf3c41b66cb62f9ec9712921202190f37/astroquery/wfau/core.py#L393) is my best guess for where the deprecated value might be specified in the code, but the query always returns both deprecated and undeprecated images.

I realize this functionality may be missing from the WFCAM archive itself, as the [web-form](http://wsa.roe.ac.uk:8080/wsa/getImage_form.jsp) does not have a `deprecated` field. Upon submitting the web-form, a table is returned that has the deprecated values for each image, and the user can manually choose to only download undeprecated images. I was wondering if anyone here has any insights on how to do this programatically through astroquery?

Start in astroquery/wfau/core.py, especially the WFAU setup near line 24 and the query construction around line 393. Compare the module's request with the WFCAM web form and its returned deprecated values, then inspect linked pull request #2809; done means establishing whether undeprecated-only retrieval can be supported and implementing or documenting the resulting behavior.

Written by the indexing model from the issue text.