Removing Unitary MetaOp (Scaling and MulCompensation)

This merge request replaces meta-operators containing only a single operation (e.g., the scaling meta-operator) with tagged multiplicative nodes.

The same approach has been applied to compensation nodes. See the related issue: #55 (moved)

Finally I moved the files PTQMetaOps.* in the operator folder and deleted every use of std::cout (replaced by Log::debug)