Store DeviceInformation inside the DeviceContext class

Store DeviceInformation inside the DeviceContext class

The device information with which the context was created is
now stored inside the DeviceContext object. This allows to pass
less arguments when information from DeviceInformation is needed
(e.g. for OpenCL optimization). The empty constructor for the
DeviceContext was also removed to make having invalid context less
probable.

Change-Id: Ie9600a89c21327246251c891807c37084f626f76