Add calc_crc32
Add pack and unpack
Implement packing for column_type
Implement abstract_column's packing (TODO: test)
Add test for abstruct_column
Implement packing for storage_base
Fix mixable_test
Split server's save and load
Implement new data format (not tested yet)
Implement packing of configuration
Implement user_data_version
Implement unimplemented pack and unpack
Check array size
Fix recommender's packing bug
Add tests for packing
Remove evil assertion
Fix mixable_holder's pack/unpack
Remove save/load interface
Fix Travis CI build failure
Fix load behavior when booted with -model_file option