Move CMake policies in common file

CMakeLists.txt

Core/CMakeLists.txt

Fit/CMakeLists.txt

GUI/CMakeLists.txt

GUI/coregui/CMakeLists.txt

Tests/Functional/GUI/CMakeLists.txt

Tests/Functional/TestMachinery/CMakeLists.txt

Tests/UnitTests/Core/CMakeLists.txt

Tests/UnitTests/Fit/CMakeLists.txt

Tests/UnitTests/GUI/CMakeLists.txt

Tests/UnitTests/Numeric/CMakeLists.txt

ThirdParty/GUI/qcustomplot/CMakeLists.txt

ThirdParty/GUI/qt-manhattan-style/CMakeLists.txt

ThirdParty/common/gtest/CMakeLists.txt

cmake/bornagain/modules/BornAgainPolicy.cmake