Add battery plugin using brass_gazebo_battery

[eborghi10]

Description

Adds a battery plugin to later integrate it with a behavior tree.

Partially fixes issue #36.

Type of change

• [X] New feature (non-breaking change which adds functionality)

How Has This Been Tested?

Please describe the tests that you ran to verify your changes. Provide instructions so we can reproduce. Also list any relevant details for your test configuration.

# Step 1
GUI=false RVIZ=true LOCALIZATION=amcl roslaunch ca_gazebo create_house.launch
# Step 2
rostopic list

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