Fixing instanceOf behaviour with WebCLObjects in test suite.

    Issue #44

    Currently we store the WebCLPlatform & WebCLDevice objects selected
    by the user in the Global singleton object. This provides the user option
    to run test suite in particular platform & Device.

    This causes issue with instanceOf operator as the actual test case is
    executed in the iFrame and the global objects are created in the MainFrame.
    Since webcl is a property of window object the instanceOf with webcl across
    frames will return false.

    Fixing this by storing metadata on the selected devices & platform, instead of actual objects.
    These metadata (index of the selected devices & platform) are used to get the particular
    objects by querying WebCL in the execution frame.

    Assumption :: Everytime we call getPlatform() & getDevices(), the implementation
    must return same array of platforms & devices in order.