Change interface names and add some materializers
Change interface names and add some materializers

Rel #149. I come up with ProcessingPrelude & MaterializationStep
names for the interfaces and implemented some of the materializers
that was already present in the column-store. This processing will
move from the column store to the query processor. Each query will
be composed from two steps represented by this two interfaces.

akumuli/Akumuli,akumuli/Akumuli,akumuli/Akumuli,akumuli/Akumuli