* Add ATTACH PARTITION FROM table for MergeTree. [#CLICKHOUSE-3546]

* Implemented replicated case on non-leader replica. [#CLICKHOUSE-3546]

* Disable merges in the dropping range. [#CLICKHOUSE-3546]

* DROP PARTITION is atomic and simpler now. [#CLICKHOUSE-3546]

* Implemented more SYSTEM queries. [#CLICKHOUSE-2931] [#CLICKHOUSE-3546]

SYSTEM queries:
RESTART REPLICAS
SYNC REPLICA db.name
STOP MERGES [db.name]
START MERGES [db.name]
STOP FETCHES [db.name]
START FETCHES [db.name]
STOP REPLICATED SENDS [db.name]
START REPLICATED SENDS [db.name]
STOP REPLICATION QUEUES [db.name]
START REPLICATION QUEUES [db.name]

* Fixed a bunch of bugs in REPLACE PARTITION. [#CLICKHOUSE-3546]

* Add tests for REPLACE PARTITION and SYSTEM. [#CLICKHOUSE-3546]

* Add system.part_log logging. [#CLICKHOUSE-3546]

* Fixed long wait in SYNC REPLICA. [#CLICKHOUSE-3546]

* Add requested changes. [#CLICKHOUSE-3546]

Fixed clickhouse-client bad return code.

* Add requested chenges. [#CLICKHOUSE-3546]

* Add requested chenges. [#CLICKHOUSE-3546]

Merge remote-tracking branch 'upstream/master' into system-log-prepare-table-on-each-flush

#2131 deleted excessive logging

Revert "#2131 deleted excessive logging"

This reverts commit d78a46d9.

Revert "SystemLog: execute prepareTable()  on each flush"

This reverts commit 7f60bb0a.

SystemLog: execute prepareTable() on each flush

* 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]

Resolves #2039

This reverts commit fcabe8b8.

This reverts commit fcabe8b8.

Fixed handling of obsolete parts.
Fixed conflict resolution between simultaneous PreCommitted covering parts.
Fixed memory leak caused by ordinary MergeTree parts stucked in Deleting state.
Added hidden _state column into system.parts.

And Removed obsolete code.

safeguards to protect against distinct partition values with the same partition_id [#CLICKHOUSE-3000]

added IDataType::updateAvgValueSizeHints; renamed PODArray::allocated_size to PODArray::allocated_bytes; renamed renamed IColumn::allocatedSize to IColumn::allocatedBytes; removed IColumn.h from IDataType.h