[rfc][icedtea-web] clean Cache

[Lukasz Dracz]

Hello,

> The change to last modified being >= 0 makes it so any-time there are
> resources sent with no last-modified header, we do not re-download unless
> FORCE policy is set. However there is no way for us to set the FORCE policy
> outside of compile-time and there is no option for the user to re-download
> without clearing cache. In this situation, it is much more sensible for us
> to just always re-download. Until we get a viable alternative to
> last-modified for figuring out when to cache things, re-downloading any-time
> we don't see the last modified is the option to go for.

Yes. I agree, I will look into the resource on http/1.1 caching Omair posted early and
see if there is anything that can be applied.

> The change to cache deletion looks okay to me.

Okay to push ?

Thanks,
Lukasz Dracz