Mention required CMake version as 3.13

bin/duneproject

@@ -346,7 +346,7 @@ Preparing the Sources
 Additional to the software mentioned in README you'll need the
 following programs installed on your system:
 
-  cmake >= 2.8.12
+  cmake >= 3.13
 
 Getting started
 ---------------
@@ -398,9 +398,7 @@ R_DELIM
 ################## CMakeLists.txt ##################
 echo "- $PROJECT/CMakeLists.txt"
 cat> "$PROJECT/CMakeLists.txt" << M_DELIM
-# 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)
+cmake_minimum_required(VERSION 3.13)
 project($PROJECT CXX)
 
 if(NOT (dune-common_DIR OR dune-common_ROOT OR

doc/buildsystem/dune-common.rst

@@ -15,12 +15,9 @@ CMake...
 - is portable
 - is controlled by ONE rather simple language
 
-Dune got support for CMake in version 2.3 alongside the old Autotools build system. It got the default in the
-2.4 release.
-
 You can install CMake through your favorite package manager or downloading source code from
 `KITWare <http://www.cmake.org>`_
-The minimum required version to build Dune with CMake is 3.1.
+The minimum required version to build Dune with CMake is 3.13.
 
 .. _howtouse: