rename the previous posix storage to posixflat and make it currently not user
selectable (since I'm not sure it's really worth using it).
The new posix storage uses the filesystem without any escaping so it's not a
real flat namespace.
This isn't a real issue since also minio is not a flat namespace and we are so
forced to use it like a hierarchycal filesystem.
On s3 limit the max object size to 1GiB when the size is not provided (-1) or
the minio client will calculate a big part size since it tries to use the
maximum object size (5TiB) and will allocate a very big buffer in ram. Also
leave as commented out the previous hack that was firstly creating the file
locally to calculate the size and then put it (for future reference).
This options is a noop on s3 but on the posix implementation it becomes useful
when there isn't the need to have a persistent file, thus avoiding some fsync
calls.
* Rename to datamanager since it handles a complete "database" backed by an
objectstorage and etcd
* Don't write every single entry as a single file but group them in a single
file. In future improve this to split the data in multiple files of a max size.
