Set VS Startup project

As supported in CMake 3.6
See http://stackoverflow.com/questions/7304625/how-do-i-change-the-startup-project-of-a-visual-studio-solution-via-cmake/37994396#37994396

Source/CMakeLists.txt

@@ -253,6 +253,7 @@ if(MSVC)
 		include_external_msproject(MBansheeEditor ${PROJECT_SOURCE_DIR}/MBansheeEditor/MBansheeEditor.csproj)
 		add_dependencies(BansheeEditorExec MBansheeEngine MBansheeEditor)
 		set_property(TARGET MBansheeEditor PROPERTY FOLDER Script)
+		set_property(DIRECTORY ${CMAKE_CURRENT_SOURCE_DIR} PROPERTY VS_STARTUP_PROJECT BansheeEditorExec)
 	endif()
 else()
 # TODO - Use Mono compiler to build the managed code as a pre-build step
@@ -279,4 +280,4 @@ set(INPUT_MODULE_LIB BansheeOISInput)
 set(PHYSICS_MODULE_LIB BansheePhysX)
 
 ## Generate config file
-configure_file("${PROJECT_SOURCE_DIR}/CMake/BsEngineConfig.h.in" "${PROJECT_SOURCE_DIR}/BansheeEngine/Include/BsEngineConfig.h")
+configure_file("${PROJECT_SOURCE_DIR}/CMake/BsEngineConfig.h.in" "${PROJECT_SOURCE_DIR}/BansheeEngine/Include/BsEngineConfig.h")