This is logically a subtask of
CASSANDRA-2710, but Jira doesn't allow sub-sub-tasks.
We need to support multiple ranges in a SliceQueryFilter, and we want querying them to be efficient, i.e., one pass through the row to get all of the ranges, rather than one pass per range.
Supercolumns are irrelevant since the goal is to replace them anyway. Ignore supercolumn-related code or rip it out, whichever is easier.
This is ONLY dealing with the storage engine part, not the StorageProxy and Command intra-node messages or the Thrift or CQL client APIs. Thus, a unit test should be added to ColumnFamilyStoreTest to demonstrate that it works.