Select CMake build type if not configured. (ros-industrial#225)

The refactored version of this driver benefits from optimalisations so selecting a build type with optimalisations enabled is important.

Only if the user hasn't configured a build type do we do this to prevent overriding whatever was already configured.

CMakeLists.txt

@@ -3,6 +3,11 @@ project(ur_modern_driver)
 
 add_definitions( -DROS_BUILD )
 
+if(NOT CMAKE_CONFIGURATION_TYPES AND NOT CMAKE_BUILD_TYPE)
+  message("${PROJECT_NAME}: You did not request a specific build type: selecting 'RelWithDebInfo'.")
+  set(CMAKE_BUILD_TYPE RelWithDebInfo)
+endif()
+
 find_package(catkin REQUIRED
   COMPONENTS
     actionlib