set_orbit: Add arbitrary stars on arbitrary orbits; add stars orbiting the black hole to a grdisc simulation; cleanup of SETUP=binary

[danieljprice]

Type of PR:
new setup

Description:

• added set_orbit functionality for setting up two body orbits using different parameter sets (current options are aeiOwf, flyby parameters and direct specification of position and velocity)
• add helper routines to set up multiple stars, to reduce lines of code needed when adding multiple stars
• fix bug where Mstar would be zero by default in the .setup file when rewritten from set_star routines
• added ability to add up to 10 stars orbiting the black hole to grdisc setup for quasi-periodic-eruption calculations
• cleanup of SETUP=binary to use new set_orbit and set_stars routines

Testing:

make SETUP=grdisc setup
./phantomsetup qpe

set nstars >= 1

./phantomsetup qpe
./phantom qpe.in

Did you run the bots? no

Did you update relevant documentation in the docs directory? no