Please describe the problem:
I noticed recently that my http cache (~/.evolution/cache/http) had
grown to almost 100MB). It appears that even though I regularly expunge
folders and empty trash, the cache does not get purged.


Steps to reproduce:
1.  view html mail
2.  delete mail, empty trash
3.  review ~/.evolution/cache/http

Actual results:
image files persist in cache

Expected results:
cached files should be purged

Does this happen every time?
yes

Other information:
Removing all folders under cache/http has no ill effects, so can be used to
purge the cache manually.

If purging is complex, perhaps offer a menu option so that users can
purge caches (this would include file attachments which may not be
purged). Purging can simply remove all sub-folders of cache/http.