Caches all favicon.ico in PNG format and use this in your blogroll.
The plugin is 100% written in PHP. In PHP it isn't possible to decode SSL sites, so the plugin try to fallback to "curl". If this is not available on your webserver, the favicon will not displayed.
No, sorry. The cache directory is currently a subdirectory in the plugin directory, I designed this to hold all together. The wordpress update installer remove the whole old plugin directory before install the update, so all cached icons will removed, too.