* 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.
* This patch adds rebuildEM tool support to work with compressed files.
* This patch increases a version of the file header.
Note: Default version of the `rebuildEM` tool was using very old API,
those functions are not present currently. So `rebuildEM` will not work with
files created without compression, because we cannot deduce some info which are
needed to create column extent.
