Use tex lookup verifier in ImageSamplingInstance

Use tex lookup verifier in ImageSamplingInstance

Simple image comparison is ill-equipped to handle all possible precision
and behavior differences (cube map corner filtering for example). This
change replaces old image comparison method with use of texture lookup
verification utilities.

Instead of rendering a reference image, texture coordinates generated by
the reference rasterizer are captured. The captured coordinates are then
used to verify the result color values retured by the implementation
using the texture lookup verification code.

This affects:
 * dEQP-VK.pipeline.image.*
 * dEQP-VK.pipeline.sampler.*
 * dEQP-VK.pipeline.image_view.*

Fixes #297
Fixes #340

Change-Id: I856000bd4d4aa7ab6c1e69af09f3655b63018b93