Call dune_enable_all_packages()

And bump required cmake version to 2.8.12.

CMakeLists.txt

-cmake_minimum_required(VERSION 2.8.6)
+cmake_minimum_required(VERSION 2.8.12)
 project(dune-gfe CXX)
 
 if(NOT (dune-common_DIR OR dune-common_ROOT OR
@@ -17,7 +17,7 @@ include(DuneMacros)
 
 # start a dune project with information from dune.module
 dune_project()
-
+dune_enable_all_packages()
 add_subdirectory("src")
 add_subdirectory("dune")
 add_subdirectory("doc")