pydata/pandas — pull request #7370 by immerrr (2014-06-06 08:13:30+00:00)
Title: ENH: change BlockManager pickle format to work with dup items

Old `BlockManager` pickle format stored items which were ambiguous and not enough for unpickling if non-unique.

After recent BlockManager overhaul, #6745, it's no longer necessary to share items/ref-items between Blocks and their respective managers, so Blocks can now be safely pickled/unpickled on their own.

Also, I've took the freedom to make the format more "extendable" by storing the state as a dictionary rather than a tuple:
```
{
"version": "0.14.1",
"axes": [ax0, ax1, ..., axN],
"blocks": [blk0, blk1, ..., blkN]
}
```

The version field is there to note the first version to implement this format.

This PR should close #7329.