On !60 CMAKE_FLAGS were replaced to CMAKE_OPTIONS since dunecontrol overrited them. These modified here were missing.

* There was a use of target_link_directories instead of target_include_directories.
* Executable targets were available but could not be compiled without its library.
* Dune dependencies are taken directly from its global variables. This enables MPI and UG_PARALLEL when necessary.
* The options file expected CMAKE_FLAGS and MAKE_FLAGS from environment, but dune-common happens to clear them before calling the options file. On this version, these are replaced by CMAKE_OPTIONS and MAKE_OPTIONS