Bug discovered by Laura. Potential as external functions and potential parameters in module pot_param.f90.

	modified:   Makefile
	renamed:    morse_pot.f90 -> f_morse.f90
	renamed:    pteller_pot.f90 -> f_pteller.f90
	renamed:    wsaxon_pot.f90 -> f_wsaxon.f90
	modified:   numerov_algorithm.f90
	deleted:    pot_param_morse.f90
	deleted:    pot_param_pteller.f90
	deleted:    pot_param_wsaxon.f90
Added gitignore and bin directory. Removed mod files in make clean.
removed compilation warning referring iflag
Added correctly the potential function as external functions, including interface block in src/numerov_algorithm.f90