Updated FTP connector documentation
Updated FTP connector documentation

volodymyr-babak/thingsboard.github.io,volodymyr-babak/thingsboard.github.io,thingsboard/thingsboard.github.io,volodymyr-babak/thingsboard.github.io,thingsboard/thingsboard.github.io,thingsboard/thingsboard.github.io,volodymyr-babak/thingsboard.github.io,thingsboard/thingsboard.github.io