message: cmake: add comments to device_plugin_container
  The doxygen comments for part of device_plugin_container need to be
  autogenerated.
diff: @@ -130,7 +130,17 @@ foreach(class_name ${plugin_class_names})
  "${FORWARD_DECLARATION_STRING}class ${impl_class_name};\n")
  set(PLUGIN_GET_STRING
  - "${PLUGIN_GET_STRING} ${class_name} &${get_name}() { return ${member_name}; }\n")
  + "${PLUGIN_GET_STRING} /**\n")
  + set(PLUGIN_GET_STRING
  + "${PLUGIN_GET_STRING} * Getter for ${class_name} plugin.\n")
  + set(PLUGIN_GET_STRING
  + "${PLUGIN_GET_STRING} *\n")
  + set(PLUGIN_GET_STRING
  + "${PLUGIN_GET_STRING} * @return a reference to the ${get_name} plugin instance\n")
  + set(PLUGIN_GET_STRING
  + "${PLUGIN_GET_STRING} */\n")
  + set(PLUGIN_GET_STRING
  + "${PLUGIN_GET_STRING} ${class_name} &${get_name}() { return ${member_name}; }\n\n")
  set(PLUGIN_MEMBER_STRING
  "${PLUGIN_MEMBER_STRING} ${impl_class_name} *${impl_member_name};\n")
  