Physics.P2.FixtureList

Allow to access a list of created fixture (coming from Body#addPhaserPolygon)
which itself parse the input from PhysicsEditor with the custom phaser exporter.
You can access fixtures of a Body by a group index or even by providing a fixture Key.
You can set the fixture key and also the group index for a fixture in PhysicsEditor.
This gives you the power to create a complex body built of many fixtures and modify them
during runtime (to remove parts, set masks, categories & sensor properties)