Add posibility to choose sim_position yaml file by circuit name

config/sim_position_full.yaml

+color1_id: green
+color1_x: 0.0
+color1_y: -2.5
+color1_z: 4.0
+color2_id: red
+color2_x: 2.5
+color2_y: -5.0
+color2_z: 4.0
+color3_id: yellow
+color3_x: -2.5
+color3_y: -5.0
+color3_z: 4.0
+color4_id: blue
+color4_x: 0.0
+color4_y: -7.5
+color4_z: 4.0
+

launch/visual_gps_sim.launch

 <!-- -->
 <launch>
 
-  <arg name="positions_file" default="sim_position_track18.yaml"/>
+  <arg name="circuit" default="full"/>
+  <arg name="positions_file" default="sim_position_$(arg circuit).yaml"/>
   <arg name="positions_path" default="$(find iri_visual_gps)/config"/>
   
   <arg name="config_yaml_file_location" default="$(find iri_visual_gps)/config"/>