Introduced dune-istl macros to find boost and fusion.

example compiles with fusion.

[[Imported from SVN: r1576]]

cmake/modules/CMakeLists.txt

+file(GLOB modules *.cmake)
+install(FILES ${modules} DESTINATION
+  ${CMAKE_INSTALL_PREFIX}/share/cmake/modules)

cmake/modules/DuneIstlMacros.cmake

+include(FindBoostFusion)

dune/istl/tutorial/CMakeLists.txt

 add_executable(example "example.cc")
+add_dune_mpi_flags(example)
+add_dune_boost_flags(example)
 target_link_libraries(example "dunecommon")