Add move-constructors to wrapper classes

This adds move-constructors and move-assignment operators
to the OpenCL wrapper classes.
Global setup for OpenCL context in tests

refs kylelutz/compute#9

device, context, and queue are initialized statically in `context_setup.hpp`.
With this change all tests are able to complete when an NVIDIA GPU is in
exclusive compute mode.

Side effect of the change:
Time for all tests to complete reduced from 15.71 to 13.03 sec Tesla C2075.