This PR seeks to bring habitat-API inline with this. StaticPointGoalSensor is now just a PointGoalSensor and the old PointGoalSensor is now a PointGoalWithGPSCompassSensor. There are also now explicit GPS and Compass sensors, such that you can fairly easily compute PointGoalWithGPSCompassSensor given [PointGoalSensor, GPSSensor, CompassSensor].
The PointGoal* sensors now also include {2d, 3d} x {Cartesian, Polar} support.

* Generalize PPO with both PointNav goal sensors
* generalize simple agents and fix lint
* Removed dataset specific nodes

* ORBSLAM2 agent refactored for new api

* Added monodepth agent