Merge branch '162-163-fix-timestamp-issues' into 'master'

Fix 2 issues in pipeline.timestamp tests (#162,#163)

for issue #162, set aspect flag when clearing images.
for issue #163, add optimal tiling feature check when creating images.
Also fix some typo.

See merge request !272

diff --cc external/vulkancts/modules/vulkan/pipeline/vktPipelineTimestampTests.cpp
Simple merge