Return Image objects on image.load
Return Image objects on image.load

In before, image.load returns what Docker API returns, which is
a text stream. This commits propose an improvement for returning
more useful information, which is a list of Image objects being
loaded.

Signed-off-by: Hongbin Lu <ac663af7588edc5fdba8b459ba8297fc182b0448@huawei.com>

vdemeester/docker-py,funkyfuture/docker-py,youhong316/docker-py,docker/docker-py,docker/docker-py,vdemeester/docker-py,youhong316/docker-py,funkyfuture/docker-py