doc: Added preliminary new chapters: environment, power and physicallayer.
Geometry: Renamed Polytope* to Polyhedron* and some cleanup.
Geometry: Cleaned up guards and added INET_API to classes.
Geometry: Moved objects, shapes and containers into separate folders.
Geometry: Cleanup.
Environment: Cleaned up object caches.
Documentation: Added more content for environment and power chapters.
Power: Added TODOs and comments.