cog: curve-of-growth creation for individual line

The cog driver generate the curve-of-growth for individual line.

Let’s look at a Si line with following parameters (and stored in file use.list):

wavelength	id	EP	loggf	C6	D0	EW
0	11040.405	14.0	6.2061	-1.449	-7.32	NaN	22.53

c = pymoog.cog.cog(5000, 4.0, 0, line_list=MOOG_run_path+'use.list')
c.prepare_file()
c.run_moog()
c.read_output()