Documenting Cache Expirations

[dsetrakyan]

Igniters,

I just noticed that Cache Expirations are not documented (probably because
they are part of the JCache spec). Nevertheless, we have documentation for
Eviction Policies [1], and I think that not having time-based expiration
policies (ExpiryPolicy) there creates an impression that we don't have it.

Can someone who knows how ExpiryPolicy works in detail document it?

[1] https://apacheignite.readme.io/docs/evictions

Thanks,
D.