Create CacheSet version that can easily be mapped over

One of the key advantages CacheSet instances exposed by Cache is the fact that stream processing done over those can be done at each individual nodes and the results are collated in the originator node.

There are situations when such CacheSet instances are to be transformed using a map() function and the resulting CacheSet needs to be exposed. Currently there's no easy way to keep a distributed cache set working as distributed while the data is transformed over.

So, this enhancement is about having an easy way to expose mapped distributed cache sets like this.