xsams2sme: fix Lade factors

[ivh]

Email from Tanya Ryabchikova, June 24, 2012:

In XSAMS VALD gives Lande-factors for the lower and the upper transition levels. In SME file we put effective Lande-factor which is a combination of the lower and upper Lande-factors and J-values:

g_eff=0.5(g_l + g_u)+0.25(g_l - g_u)(J_l(J_l+1) - J_u(J_u+1))

We calculate g_eff in PRESELECT stage and add it to VALD short output format which is eqiuvalent to SME format. It means that you have to calculate it, too , creating SME-output. It should be placed after Van der Waals constant, which is absent, too. The whole sequence is:

'Elem',Wavelength,Excit(eV),Vmic(0.0),log(gf),Rad,Stark,VdW,g_eff,Depth(0.0)'Comment'