1. Add two new exception types: AdlsFileAlreadyExistsException and AdlsBadOffsetException
2. Add optional offset to append
3. Fix columns in TableType to be a list of typefieldinfo
4. Fix bug in DataLakeStoreFrontEndAdapterImpl to properly create a file with just the data being passed in and not the full 4MB array (even if the back of the array is empty).
5. fix the uploader tests to include a < 4mb file upload test