Create a new sequence structure by loading the information from the directory.
directory: Path to the sequence directory.
varargin[Name]: Name of the sequence. By default the name of the directory is taken as the name of the sequence.
varargin[Mask]: File pattern for images. By default '%08d.jpg' is used.
varargin[Dummy]: Create the sequence structure without checking if all the images exist.
varargin[Start]: The number of the first frame in the sequence (1 by default).