Putting some structure in the storage engine

Apache Cassandra 3.0 introduced a significant refactor of its storage engine, with changes made to better align the internal structure of objects manipulated by the storage structure with what is exposed through CQL (Cassandra Query Language). The new Map<byte[], SortedMap<Clustering, Row>> structure replaces the old Map<byte[], SortedMap<byte[], Cell>>. This change allows for more efficient handling of deletions and a more compact storage format. Additionally, the use of COMPACT STORAGE is discouraged in C* 3.0 as it no longer offers any advantages over non-compact tables.