Add a list of labels to set as classes

Necessary to understand how the qcnn learns with more problematic classes. Examples:
8 classes: `labels = ['Annual Crop', 'Forest',
                  'Highway', 'Industrial',
                  'Pasture',
                  'Residential', 'River',
                  'SeaLake']`
5 classes: `labels = [ 'Forest',
                  'Highway', 'Industrial',
                  'Pasture', 'River',]`