disable fp64 tests if extension not available
updated code and tests if fp64 available or not
remove invalid test case when creating memory objects from HTML5 ImageData
if KHR_fp16 is not available on any device, test is not run.
forgot a parameter to select FP16 device
moved select_fp16_device and select_fp64_device to clUtils
Merge pull request #90 from mikeseven/master

disable fp64 tests if extension not available