implement basic self-driving mode

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implement a controller which uses the sensor data (LIDAR, etc.) to figure out a path where the robot should drive.

requires #8 to implement and either #10 or #12 to actually test it.

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it seems that we don't necessarily need to implement this ourselves, instead there are things like amcl which we might be able to use.

we can also have a look at what linorobot is doing.

and there's a video which i haven't watched yet.

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Paula recommended having a look at hector_exploration_planner (we could potentially use hector_exploration_node directly)

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for a simple "drive where i tell you" we could also follow this tutorial and use the move_base package