Merge branch 'duneproject-cmake-3.1' into 'master'

Require CMake 3.1 when creating new modules with duneproject.

See merge request core/dune-common!429

bin/duneproject

@@ -384,7 +384,9 @@ R_DELIM
 ################## CMakeLists.txt ##################
 echo "- $PROJECT/CMakeLists.txt"
 cat> "$PROJECT/CMakeLists.txt" << M_DELIM
-cmake_minimum_required(VERSION 2.8.12)
+# We require version CMake version 3.1 to prevent issues
+# with dune_enable_all_packages and older CMake versions.
+cmake_minimum_required(VERSION 3.1)
 project($PROJECT CXX)
 
 if(NOT (dune-common_DIR OR dune-common_ROOT OR