Refactor. Use decorators for skipping cuda-only-tests.
Unpickle cudaNdarray as numpy.ndarray, if cuda is not enabled.

However, emit a warning.
Create test file for type test and move test case.
Revert "Refactor. Use decorators for skipping cuda-only-tests."

There is no more use for choosing single tests to skip.

This reverts commit 99295012bafccf637b6ad846c9f8719f4ebca1d1.
Fix typo.
Add config flag experimental.unpickle_gpu_on_cpu.

Allows unpickling gpu cudaNdarray as numpy.ndarray.
See AddConfigVar comment for more details.
Fix test.
Add assertion message.
Surround by try-finally to eventually reset flag properly.
Merge pull request #1734 from herr-biber/nocuda-unpickle-cudandarray-as-nparray

Unpickle CudaNdarray as numpy.ndarray, controlled by an experimental flag.