Fix missing spice call for body[8] in first runs.
Caused unnecessary time steps in the beginning.
Misc. cleanup of RK76:
- remove body[9] (not needed since always identical to body[8]
- Comments, formatting
Major fix of Integrator:
- Wrong sign in equation caused major error.
- Interpolation formula was mis-optimized earlier.
(- Better commenting)
Merge branch 'md_RK76' into GSOC-Integrator

Conflicts:
	Particle_Integrator/Code/Integrators/RungeKutta67.h