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

Better --fof help string and prevent the code from running with black holes seeding if the black holes policy has not been chosen.

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.

Increased version number following the addition of star-formation and feedback jointly over MPI, black hole accretion and feedback (also over MPI), refactoring of the hydro parameters, improvement to the memory footprint and completion of first fully-fledged EAGLE runs.

Added loop over the FOF groups to create black holes. Still need to allocate space for the black holes.

Destroy the runners cleanly when shutting down the engine.

Closes #559

See merge request !819

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.

Added a run label to the parameter file that gets written to the snapshot headers.

See merge request !817