love.physics: simplify Body and Shape API.

#1130

- Shapes are now directly attached to Bodies when they're created (similar to love 0.7 and older).
- Fixtures are removed.
- All methods that were in Fixtures now exist in Shapes.
- All APIs that used or returned a Fixture now do the same with a Shape.

- Add new love.physics.new*Shape variants that take a Body as the first parameter.
- Deprecate the new*Shape APIs that don't take a Body.
- Deprecate love.physics.newFixture (the deprecated function now returns a Shape).
- Replace Body:getFixture and Body:getFixtures with Body:getShape and Body:getShapes (Body:getFixtures is deprecated).
- Replace World:queryFixturesInArea and World:getFixturesInArea with World:queryShapesInArea and World:getShapesInArea (queryFixturesInArea is deprecated).
- Replace Contact:getFixtures with Contact:getShapes (Contact:getFixtures is deprecated).
- Replace all love.physics callback Fixture parameters with Shape parameters.
- Deprecate ChainShape:getChildEdge.

src/modules/physics/box2d/ChainShape.h

@@ -45,7 +45,7 @@ public:
 	 * Create a new ChainShape from a Box2D chain shape.
 	 * @param c The chain shape.
 	 **/
-	ChainShape(b2ChainShape *c, bool own = true);
+	ChainShape(Body *body, const b2ChainShape &c);
 
 	virtual ~ChainShape();