#568 RLE Lossless encoding errors

[XXX]

Hi Mathieu, Dave Clunie created an issue on pydicom about an RLE Lossless dataset being encoding with odd-length segments, however the standard requires even-length. I had a look at RLECodec::Code() but couldn't seem to find anything that indicates padding is being added to segments, although I could definitely have missed it.

Secondly, and I'm not sure if you explicitly support big endian architectures, but on such hardware looks like the RLE header is encoded using big endian values instead of little endian.

Finally, and again on big endian architectures, are the RLE segments for multi-byte values in the correct order? I'm not really sure what endianness is expected when on big endian arch when ImageChangeTransferSyntax() is called, but with a little endian dataset I assumed little endian ordered Pixel Data would make sense given it's consistent with the Transfer Syntax. However in that case the segment order is LSB first instead of the required MSB first.

Thanks