Previously each device adapter only had a unique string name. This was
not the best when it came to developing data structures to track the status
of a given device at runtime.
This adds in a unique numeric identifier to each device adapter. This will
allow classes to easily create bitmasks / lookup tables for the validity of
devices.
When writing multiple backend code users of vtkm need to use the
DeviceAdapterTraits classes, so therefore we should move them to vtkm::cont
to signify this.
Array transforms can now be created with an inverse functor, allowing for
casts back into the native array type. As a result, array transforms with
both a functor and inverse functor defined can perform read and write
operations. As an example, ArrayHandleCast now supports this operation. The
original implementation of ArrayHandleCast (i.e. read only) has been renamed
'ArrayHandleCastForInput'.
