WIP: new cmake build system

Summary

• Separate cmake files instead of one big DuneMacros.cmake !957 (closed)
• Give all cmake functions the prefix dune_ (included in !957 (closed))
• Add argument to dune_project(<target>) to allow creation of a module library directly
• Remove global include_directories in favor of target_include_directories !944 (closed)
• Link tests created by dune_add_test automatically against module library
• Remove the cmake module include CMakeParseArguments !1008 (merged)
• Remove the cmake variable DUNE_DEFAULT_LIBS !1009 (merged)
• Simplify dune_library_add_sources by using target_sources !1010 (merged)
• Simplify enforcement of required c++ standard in cmake !862 (merged)
• Simplify functions from DuneModuleDependencies.cmake !1249 (merged)
• Set CMAKE_MODULE_PATH in <module>-config.cmake !1038 (closed)
• Move include(DuneModules) into dune-common-config.cmake
• Remove pkg-config support for finding dune packages (was not working before and not used. May be activated later again)
• Extract version of module dependencies from package file (instead of the dune.module file)
• Remove dune_enable_all_packages from default dune project

Superbuild

In order to build several modules in one run, prepare a CMakeLists.txt file in the root directory of all dune modules:

cmake_minimum_required(VERSION 3.13)
project(dune VERSION 2.9 LANGUAGES CXX)

set(dune_modules dune-common dune-geometry dune-localfunctions dune-uggrid dune-grid dune-istl)

set(CMAKE_PREFIX_PATH ${PROJECT_BINARY_DIR})
set(CMAKE_MODULE_PATH ${PROJECT_SOURCE_DIR}/dune-common/cmake/modules)
set(DUNE_DISABLE_SIMD_TESTS TRUE)

enable_testing()
foreach (mod ${dune_modules})
  add_subdirectory(${mod})
endforeach(mod)

include(FeatureSummary)
feature_summary(WHAT ALL)