Gravity brute force checks, extra options

See merge request !1014

Updated RTD as per your recomendations.

Added ForceChecks to paramater_example.yml

Changed brute_force_gravity_flag to force_checks_snapshot_flag

Removed epsilon from gravity_exact_force_file_exits

Made functions in src/kernel_long_gravity.h double

Planetary documentation

Closes #659

See merge request !1038

Quick lyman alpha module

See merge request !1036

Don't attempt to repartition when restarting, we don't have any task times until…

Closes #658

See merge request !1034

Don't attempt to repartition when restarting, we don't have any task times until the first real step runs

Fix bug in multiple BH mergers

See merge request !1033

Use the correct unit conversion factor for the maximal temperature times in the non-cosmological EAGLE tracers.

Sf crash if no star

See merge request !1030

Give a sensible DM softening also for runs without DM

Closes #656

See merge request !1031

Updated the internal units of all the main boxes to reflect the internal constants assumed by the code.

Updated the internal units of all the main boxes to reflect the internal constants assumed by the code.