PE-1663 - Preparation for multi-column ranges for ident and group-by
columns.

Extended the PrivateRange.ColumnVectorRanker to also compare on the
average size of column types in the vector.
Merge branch 'master' of git@github.com:Tesora/tesora-dve-pub.git
PE-1663 - Added support for column tuples to ident and group by columns.
Ident columns are treated individually by default but that can be
changed with the USE_IDENT_TUPLES analyzer option.
PE-1663 - Got rid of SingleColumnRanker so that that all PrivateRange
column scoring is done by the same code.