Implementations of apply(), by(), eapply(), lapply(), Map(),
.mapply(), mapply(), replicate(), sapply(), tapply(), and vapply()
that can be resolved using any future-supported backend, e.g.
parallel on the local machine or distributed on a compute cluster.
These future_*apply() functions come with the same pros and cons
as the corresponding base-R *apply() functions but with the additional
feature of being able to be processed via the future framework.
