[3pwaterpoil] Add missing CMakeLists.txt and install headeres

dumux/porousmediumflow/3pwateroil/CMakeLists.txt

+
+#install headers
+install(FILES
+indices.hh
+localresidual.hh
+model.hh
+primaryvariableswitch.hh
+volumevariables.hh
+vtkoutputfields.hh
+DESTINATION ${CMAKE_INSTALL_INCLUDEDIR}/dumux/porousmediumflow/3pwateroil)

dumux/porousmediumflow/CMakeLists.txt

@@ -7,6 +7,7 @@ add_subdirectory("2p2c")
 add_subdirectory("2pnc")
 add_subdirectory("2pncmin")
 add_subdirectory("3p")
+add_subdirectory("3pwateroil")
 add_subdirectory("3p3c")
 add_subdirectory("co2")
 add_subdirectory("compositional")