WebCL Conformance test suite update for review.

    Fixes the below issues ::
    [Khronos #47] getInfo(DEVICE_QUEUE_PROPERTIES) test should expect 0, not null
    [Khronos #46] getInfo(DEVICE_VENDOR_ID) test should expect a number, not a string
    [Khronos #51] bindingTesting/eventsAndCallbacks/cl_event_setCallback.html review
    [Khronos #50] bindingTesting/eventsAndCallbacks/cl_webcl_waitForEvents.html review
    [Khronos #36] Need tests to ensure OpenCL C 1.2 features are not accepted.
    Add testcases to verify invalid callbacks, expecting typeError
    Add test cases for Valid values for parameters.
    Add testcase to verify IMAGE_FORMAT_MISMATCH

    Contributors :
    SRI-B : Shilpa Shri, Sharath Kamath, Gajendra N.
    SRA : Antonio, Steven and Igor.