Restructure information exchange for integrators:
- integrators receove struct pointer instead of variables
- include information that is needed for PRD calculation
PRD implementation:
- Calculate particle-constant part of PRD in separate function
- Main calculation in calc_accel
- Print out particle radius and add it to the configuration_values struct
- Add CMake option for PRD
Merge branch 'md_PRD' into GSOC-Integrator
Hand over some calc_accel arguments using struct pointer
- should be faster
- more compact call and easy access to all configuration values if needed without clutter in the function call
Add option for stationary centered bodies
- useful for testing algorithms and physics
- all bodies will be kept at (0,0,0)
Change option for stationary centered bodies to runtime option
- uses function pointers for spkezp_c
- easier to control
- does not seem to harm performance
Merge branch 'GSOC-Integrator' into md_PRD
Changes aiming to improve accuracy of PRD
- Re-calculate speed vector during PRD calculation based on substep information
Bugfix for previous commit: Nonexistant time value
Merge branch 'md_PRD' into GSOC-Integrator
Merge branch 'master' into GSOC-Integrator
Merge branch 'GSOC-Integrator'