Add very simple in-memory compression interface that works directly for columns.

Add method IColumn::compress. It returns either:

• CompressedColumnPtr that is shared_ptr of ICompressedColumn, that has the only method virtual ColumnPtr decompress();
• std::function<ColumnPtr()> - a function object to get decompressed column back;

This method will take no parameters for compression but it can be extended later.

It should compress the whole buffers of columns as a single block with lz4. The usual compression interface with Read/Write buffers, support for checksums, etc. is not used.

Add support for SETTINGS clause for Memory table with the setting compress = 0|1.

The hypothesis is that compressed Memory tables will work faster on SELECTs by using less memory bandwidth.
Actually we already confirmed this hypothesis with MergeTree tables: they are compressed by default and it works faster than with disabled compression even if data is in memory and disk is not used.