RFC: Proposed battery message and arming service

[Tully Foote]

Hi Everyone,

We're working toward putting together a demo using the standard interfaces.

As a first step we've proposed a new BatteryState message in sensor_msgs https://github.com/ros/common_msgs/pull/74

And have started a PR to discuss a service for arming mavs for flight: https://github.com/ethz-asl/mav_comm/pull/25 The PR is not ready to be merged but presented as a strawman.

Please take a look and provide any comments you have.

Tully