Add new battery plugin

[eborghi10]

Description

This PR replaces the old battery plugin by a simpler implementation.

Type of change

Please delete options that are not relevant.

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

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.

# Start robot simulation
HIGH_BATTERY_CONSUMPTION=true GUI=false RVIZ=true LOCALIZATION=amcl roslaunch ca_gazebo create_house.launch
# Start behavior tree
roslaunch ca_behavior_tree bt.launch
# Echo battery voltage topic
rostopic echo /create1/battery/voltage

Test Configuration:

• [ ] Real robot
• [X] Gazebo simulation
• [ ] Other (please specify)

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