INT-3200: DefaultSFTPSessionFactory supports using a ByteArrayResource f...

DefaultSFTPSessionFactory supports using a ByteArrayResource for the PrivateKey
@liujiong1982 Here are my STS save actions...

![screen shot 2014-07-30 at 7 42 04 pm](https://cloud.githubusercontent.com/assets/483832/3758165/348d9328-1843-11e4-9314-0b10ff8a5f66.png)