vtkhdf5: Remove extra calls to cmake_minimum_required

Drop calls to this command in subdirectories.  They are never used as
the top-level source directory.

Change-Id: I6249719417ea8adb9297fab9f7e969c944bb3a13
Accelerators/Dax: Remove extra call to cmake_minimum_required

This directory is never used as the top-level source.

Change-Id: Id3878915df82c6e69323af625cc5d3906629faf4
Refactor top-level CMake Policy settings as loop

Use a loop in the top-level CMakeLists.txt file to set policies, and
comment each item with the version of CMake that introduced it.
Also do this in Testing/External/CMakeLists.txt since that is used
as the top-level source tree for building tests externally.

Change-Id: Ic4f0fab6f23d1409ad1140617292f2751896540f
Examples: Set required CMake version and policies before project()

Update CMakeLists.txt files in the Examples to call the
cmake_minimum_required() command and set policies before calling the
project() command.  This is necessary because policies may affect
the project() command behavior.

Change-Id: Id7d4e68b35fabdff29c1ecb0b9e7475e5588b753
Set CMake Policies CMP0025 and CMP0042 as necessary

CMake 3.0 introduces these policies to improve default behavior on OS X.
Set them explicitly in VTK to avoid policy warnings.  VTK already works
with the NEW behavior.

Policy CMP0025 affects the project() command when the Apple Clang
compiler is used so we need to set it in all the Examples.  Policy
CMP0042 affects shared libraries on OS X, enabling MACOSX_RPATH by
default.  Set it in directories where we create libraries.  Also tell
KWSys to enable MACOSX_RPATH explicitly instead of setting the policy.

Change-Id: I543b60ee1b8f629adb150e01ee83d99dddb66f46
Merge topic 'fix-CMP0025-CMP0042-warnings' into master

2ad9f474 Set CMake Policies CMP0025 and CMP0042 as necessary
3a04542c Examples: Set required CMake version and policies before project()
59836055 Refactor top-level CMake Policy settings as loop
08df7a88 Accelerators/Dax: Remove extra call to cmake_minimum_required
ee1c7530 vtkhdf5: Remove extra calls to cmake_minimum_required