Changes in SETUP= masstransfer

[analulujg]

Type of PR:
modification to existing code

Description:
Changes in steup_masstransfer.f90:

• Add flag 'sink_off' to replace sink particles with fixed gravitational potentials
• Add flag 'use_mesa_file' to change between mass transfer rate constant or get mass transfer rate from mesa file (variable mdot)

Changes in injection_masstrasfer.f90:

• New subroutine 'read_masstransferrate' in module readwrite_mesa
• New way of injecting particles due to variable mdot.
• When using gravitational potentials, we have added delete subroutine inside radius to simulate accretion.

Testing:
~/phantom/scripts/writemake.sh masstransfer > Makefile
make; make setup
./phantomsetup mt.setup
./phantom mt.in
Use file for variable mdot: test_data.txt

Did you run the bots? no

Did you update relevant documentation in the docs directory? no