Added VkImageView object.
Added "clear" function to illustrate the link between VkFramebuffer
attachments, VkImageView and VkImage, along with the minimal set of
class members to allows the function arguments to be used properly.

Bug b/119620767 b/119621736

Change-Id: I0e7e6017979960bacbdf888d632c83edda3483cf
Reviewed-on: https://swiftshader-review.googlesource.com/c/22668Tested-by: Alexis Hétu <sugoi@google.com>
Reviewed-by: Chris Forbes <chrisforbes@google.com>