Added support for blacklisting paths for caching

[dmattia]

This is related to #62

[aknysh]

@dmattia thanks for the PR.
I think it would be better to provide an cache_behaviors var and then contract ordered_cache_behavior block from it.
Otherwise we are using that block just for blacklisting, which applies to a limited set of use-cases.

[dmattia]

I can make that change! I'd love to talk about your opinions on the var types though.

The default_cache and ordered_caches are almost entirely the same, except the default cache doesn't have a path option (at least that's my understanding).

So my thought was that we would leave the existing cache vars as they are, updating their docs to specify that they are only for the default cache. And then the ordered_caches would have a var.ordered_cache_behaviors where clients would have to pass in a large array of object with fields related to caching stuffs.

So basically what you said, but with var.ordered_cache_behaviors instead of var.cache_behaviors. Does that sound okay?

[dmattia]

I created #70 to more generally support ordered caches

[dmattia]

I believe it would be possible to support both PRs, but will leave it up to you guys to determine if you think that would be too much

[maximmi]

@dmattia let's stick to more general way! thanks for your contribution