* Adds CompressInterfaceLZ4 which uses LZ4 API for compress/uncompress.
* Adds CMake machinery to search LZ4 on running host.
* All methods which use static data and do not modify any internal data - become `static`,
so we can use them without creation of the specific object. This is possible, because
the header specification has not been modified. We still use 2 sections in header, first
one with file meta data, the second one with pointers for compressed chunks.
* Methods `compress`, `uncompress`, `maxCompressedSize`, `getUncompressedSize` - become
pure virtual, so we can override them for the other compression algos.
* Adds method `getChunkMagicNumber`, so we can verify chunk magic number
for each compression algo.
* Renames "s/IDBCompressInterface/CompressInterface/g" according to requirement.
MCS now chowns created directories hierarchy not only files and
immediate parent directories
Minor changes to cpimport's help printout
cpimport's -f option is now mandatory with mode 2
Fixes the following:
* Compression ratio calculation was incorrect
* Possible issues due to system catalog thread ID usage
* Compressed file size data count was leaking many FDs when the table
wasn't compressed
* Compressed file size data count was allocating random large amounts
of RAM and then leaking it when the table wasn't compressed
* Add INFORMATION_SCHEMA.COLUMNSTORE_FILES which contains information
about files
* Remove file information from COLUMNSTORE_EXTENTS (due to above)
* Hide columns with Object ID < 3000 (internal columns)
* Fix bad calculation in data_size columns
* Fix minor memory leak
* Add compressedSize() function to IDBFileSystem to get the used file
size for a compressed file
* Add columnstore_info schema with utility stored procedures to access
the information_schema tables
