Feature/add examples to testsuite

Depends on !74 (merged) to be merged.

examples/CMakeLists.txt

-add_executable(elementparametrization elementparametrization.cc)
-target_link_libraries(elementparametrization ${DUNE_LIBS})
-
-add_executable(parametrized-refinement parametrized-refinement.cc)
-target_link_libraries(parametrized-refinement ${DUNE_LIBS})
+dune_add_test(SOURCES elementparametrization.cc)
+dune_add_test(SOURCES parametrized-refinement.cc)