SINGA-323 Add method to resize images by given width and height
SINGA-323 Add method to resize images by given width and height

Add methods to resize images by given width and height, named as
resize_by_hw, resize_by_hw_list, resize_by_hw_range;
Encapsulate original "resize" methods into "scale" methods.

apache/incubator-singa,apache/incubator-singa,apache/incubator-singa,apache/incubator-singa,apache/incubator-singa