Merge branch navigation into melodic.

diff --cc twil_gazebo_ros_control/package.xml
index 7723f91,7723f91..f429581
--- 1/twil_gazebo_ros_control/package.xml
--- 2/twil_gazebo_ros_control/package.xml
+++ b/twil_gazebo_ros_control/package.xml
@@@ -52,21 -52,21 +52,21 @@@
    <buildtool_depend>catkin</buildtool_depend>
    <build_depend>control_toolbox</build_depend>
    <build_depend>controller_manager</build_depend>
--  <build_depend>gazebo</build_depend>
++  <build_depend>gazebo_ros</build_depend>
    <build_depend>gazebo_ros_control</build_depend>
    <build_depend>pluginlib</build_depend>
    <build_depend>roscpp</build_depend>
    <build_depend>twil_description</build_depend>
    <build_export_depend>control_toolbox</build_export_depend>
    <build_export_depend>controller_manager</build_export_depend>
--  <build_export_depend>gazebo</build_export_depend>
++  <build_export_depend>gazebo_ros</build_export_depend>
    <build_export_depend>gazebo_ros_control</build_export_depend>
    <build_export_depend>pluginlib</build_export_depend>
    <build_export_depend>roscpp</build_export_depend>
    <build_export_depend>twil_description</build_export_depend>
    <exec_depend>control_toolbox</exec_depend>
    <exec_depend>controller_manager</exec_depend>
--  <exec_depend>gazebo</exec_depend>
++  <exec_depend>gazebo_ros</exec_depend>
    <exec_depend>gazebo_ros_control</exec_depend>
    <exec_depend>pluginlib</exec_depend>
    <exec_depend>roscpp</exec_depend>