Improve CMake module
Some improvements to VTKmConfig.cmake and the device configuration scripts to better support CMake projects using VTK-m.
See merge request !271
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'.
This is needed as it allows the policies specified in the root of
vtk-m to propagate properly to the examples. When CMake
sees a cmake_minimum_required command it resets all policy flags.
