Navigation + MavROS integration

[rland93]

I believe we can replicate most of the functionality offered by qGroundControl with MavSDK:

https://mavsdk.mavlink.io/main/en/index.html

This would allow us to use qGroundControl only to observe ongoing missions, not to actually push commands to the drone.

It seems easy to do this; mavSDK has a couple of one-liners.

So my goal is to:

1. setup and document setup of MavSDK + PX4 Simulation
2. run PX4 simulation successfully on a simple MavSDK mission:

• takeoff
• go through a couple waypoints
• land

3. run PX4 simulation where MavSDK is commanding the drone and its flight path and telemetry are being viewed by qGroundControl

Not sure if (3) can be done with simulation, but this would be the foundation for integrating navigation moving forward.

[rland93]

Scratch all that about MavSDK. ROS stays king.

We are going to use MAVROS commands to run missions on the drone. I am calling the node that runs missions gnc.

Scaffold is hopefully up in a couple hours in the ROS-dev branch.

[rland93]

214cd2b

Produced an open-loop path in simulation:
https://www.youtube.com/watch?v=F3Sf8A3bIR0

[rland93]

I'm going to merge this into ROS-dev, but I'm keeping the issue open until we have a better UX for putting missions in.