SDK does not allow empty string PartitionKey or RowKey values

[christophercurrie]

The AtomPubParser prevents PartitionKey or RowKey from being an empty string.

However, MSDN has an article that states:

Each PartitionKey and RowKey properties are allowed to store up to 1 KB of string values. Empty strings are also allowed however null values are not.

The restriction in the SDK should be removed.

[JThinkable]

This is still an issue as of 0.4.2.

[gcheng]

move to storage's repo.