* column size calculating routines now take into account multiple streams [#CLICKHOUSE-2831]

* rename for clarity

* use more appropriate method for calculating table size

* add info about total uncompressed part size to system.parts and system.parts_columns [#CLICKHOUSE-2831]

* rename columns for clarity [#CLICKHOUSE-2831]

* count shared substreams only once [#CLICKHOUSE-2831]