Documentation fixes.

Fix documentation comments in FunctionInterface.h and some declarations
that are only for documentation in DeviceAdapterAlgorithm.h.
Merge branch 'documentation-fixes'
Update the documentation to note have references to dax.
Update the documentation to use vtkm::FloatDefault instead of vtkm::Scalar.
Merge branch 'remove_references_to_dax'
move DeviceAdapterAlgorithm to correct folder as it's namespace
Adding a cuda device adapter to vtkm.

Porting the dax device adapter over to vtkm. Unlike the dax version, doesn't
use the thrust::device_vector, but instead uses thrust::system calls so that
we can support multiple thrust based backends.

Also this has Texture Memory support for input array handles. Some more work
will need to be done to ArrayHandle so that everything works when using an
ArrayHandle inplace with texture memory bindings.