Add IMU plugin with Tf prefix for frame ID

[eborghi10]

Description

With the intent of removing the current way of setting the TF prefixes, this PR modifies the default IMU plugin to add a Tf prefix to the Frame ID field.

Type of change

• [X] Bug fix (non-breaking change which fixes an issue)
• [X] Breaking change (fix or feature that would cause existing functionality to not work as expected)

How Has This Been Tested?

roslaunch ca_gazebo create_empty_world.launch
rostopic echo /create1/imu/data/header

Test Configuration:

• [ ] Real robot
• [X] Gazebo simulation

Checklist:

• [X] My code follows the style guidelines of this project (Travis CI is passing)
• [X] I have performed a self-review of my own code
• [X] I have commented my code, particularly in hard-to-understand areas
• [X] I have made corresponding changes to the documentation
• [X] My changes generate no new warnings
• [X] I have added tests that prove my fix is effective or that my feature works
• [X] New and existing unit tests pass locally with my changes