Support bumper sensors in Gazebo

[sasilva1998]

Description

• Added the support for bumper sensor for each of the iRobot Create versions. The contact with the bumpers is checked according to the mesh of the corresponding bumper shape for each robot. For that I added a new arg version in create_description/urdf/create_base.urdf.xacro.
• Unfortunately, since there is no plugin for Omni IR, could only add a the common IR from Gazebo which I hope is still of use.
• Generated a package with a minimal example to simulate the different Create robot version. Also updated the Readme to specify how to run the simulation. Uses a world file from turtlebot3_gazebo.
• Added the publish of transforms for the wheels.

This PR is connected to #76.

Test configuration
ROS version: Noetic

[jacobperron]

Thanks for the additions!

See my feedback below.

[jacobperron]

I have mixed feelings about adding a simulation-specific package. The package is not providing any custom simulation plugins or configuration; it is simply an example launch file and rviz config file. I think it makes more sense to simply move those into create_bringup (which is the package meant for example launch/config files). While I think having the examples are nice, it technically introduces a runtime dependency on Gazebo, which I'd rather avoid.

It might be best to keep these examples in a separate repository.

[sasilva1998]

Hi @jacobperron, sorry for the late response and thanks for your comments. I have made the recommended changes.

[jacobperron]

Thanks for the contribution!