The legacy VTK reader sometimes has to permute cell data because some
VTK cells are not directly supported in VTK-m. (For example, triangle
strips are not supported. They have to be converted to triangles.)
The global and petigree identifiers were not properly getting permuted.
This is now fixed.
The enumerations in `vtkm::cont::Field::Association` were renamed in the
previous commit. The old names still exist, but are deprecated. Change
the rest of the code to use the new names.
There were several places in the code that had to check the type of an
`UnknownArrayHandle` and conditionally get or copy that array. This code
is simplified by using `ArrayCopyShallowIfPossible`.
`VaraintArrayHandle` has been replaced by `UnknownArrayHandle` and
`UncertainArrayHandle`. Officially make it deprecated and point users to
the new implementations.
C++11 introduced the `std::vector::data()` method. In addition to being
more syntatically pleasing, it should correctly handle the condition
when the `std::vector` is size 0 and therefore has no real pointer.
(Expressions like `&v[0]` are undefined when the `vector` is empty.)
Most of this code is not templated methods. Rather, it implements over
several types to call templated functions, which creates quite a bit of
code. Rather than have all code using a reader recompile the code, just
compile it once and put it in a library.
