Transition to VTK 8.0

Regarding

Actually, it wouldn’t be completely crazy to go straight to C++14…

  • Windows: in the past, Visual Studio was always lagging, but we will be requiring MSVC19 (Visual Studio 2015) anyway, which supports everything in C++14.

  • Mac: Clang has supported everything in C++14 for more than two major releases.

  • Linux is the wildcard, because of old clusters. However, they are not any worse off than will be with C++11 – they have to use devtoolset or the equivalent anyway.

@pieper @lassoan