Add master_big stl and world

worlds/master_big.world

+<?xml version="1.0" ?>
+<sdf version="1.4">
+  <world name="master_big">
+    <!--
+    <include>
+      <uri>model://sun</uri>
+    </include>
+    -->
+    
+    <light type="directional" name="sun">
+      <cast_shadows>true</cast_shadows>
+      <pose>0 0 10 0.2 0.2 0.2</pose>
+      <diffuse>0.8 0.8 0.8 1</diffuse>
+      <specular>0.2 0.2 0.2 1</specular>
+      <attenuation>
+        <range>1000</range>
+        <constant>0.9</constant>
+        <linear>0.01</linear>
+        <quadratic>0.001</quadratic>
+      </attenuation>
+      <direction>-0.5 0.1 -0.9</direction>
+    </light>
+
+    <include>
+      <uri>model://ground_plane</uri>
+    </include>
+
+    <model name="master_big">
+      <static>true</static>
+      <link name="link">
+        <pose>0 0 0 0 0 0</pose>
+        <collision name="collision">
+          <geometry>
+            <mesh>
+              <uri>model://meshes/master_big.stl</uri>
+              <scale>1 1 1</scale>
+            </mesh>
+          </geometry>
+        </collision>
+        <visual name="visual">
+          <geometry>
+            <mesh>
+             <uri>model://meshes/master_big.stl</uri>
+              <scale>1 1 1</scale>
+            </mesh>
+          </geometry>
+        </visual>
+      </link>
+    </model>
+    
+<gui fullscreen='0'>
+      <camera name='user_camera'>
+        <pose frame=''>10.0958 -9.41664 10.969 0 0.667643 2.2282</pose>
+        <view_controller>orbit</view_controller>
+        <projection_type>perspective</projection_type>
+      </camera>
+    </gui>
+
+  </world>
+</sdf>
\ No newline at end of file