Used QuadTree::insert_all for integrator.
Faster compilation time by building static library.
Modified Simulation's timestep routines.
More testing and debugging of LeapfrogKDKIntegrator.
Combined BasicBody and Body for simplicity.
Work in progress conversion to use std::shared_ptr<Body> instead of Body for QuadTree.
Framework uses shared_ptr<Body>, still need to convert testing.
Acceleration calculation now skips cases where the two bodies are one and the same.