Only call engine_rebuild() and not engine_init_particles() in main_fof. We don't need the full thing.

Remove the option of a dry run. Print the number of BHs read in on startup. Do not print the number of seeds to create in the fof_dump_data() function.

Changed the way we set the run frequency to use a physical simulation time rather than a fixed number of steps.

Move the activation of FOF tasks to a separate function. Make a separate function call for the splitting of FOF tasks. Do not reset the unlocks or weights of tasks in engine_make_fof_tasks(); they are not used for FOF tasks and mess up the rest of the tasks.

add a new engine_step_prop_stop which makes the runners quit if set. engine_clean now sets the prop, releases the runners, and pthread_waits on them.

General style improvement and documentation of the core FOF routines. Do not pass the 'space' structure into the routines to avoid indirections.

Added communication functions to propagate the new number of star particles after a SF event has occured.