Added GetSeriesCount method

The itkSCIFIOImageIO can now be queried for the total number of series
in a dataset, via the GetSeriesCount method.
Account for RGB channel count when reading

The itkSCIFIOImageIO will now properly count the number of bytes to read
by considering the RGB channel count.
Added allSeries flag to SCIFIOImageIOTest

Can now specify -a or --all to automatically process all series in a
dataset.
Cleaned up series code

Used reader->UpdateOutputInformation to read image info before getting
to Writer->Update(). This allows the series information to be
updated/queried in a more straightforward way, instead of waiting for a
Writer update to populate the io's reader.
Enhanced exception handling

The itkSCIFIOImageIO will now differentiate between exceptions and
failing commands, and print an appropriate message before terminating.