Add polarized Lb->Lll angular coefficients

[anjabeck]

Hi!

This PR adds the angular coefficients arising in Lb->Lll for polarized Lb baryons. They are given in arxiv:1710.00746.

• The default polarization is the Lb polarization when the bbar pair is produced from a Z decay as measured at LEP (assuming most studies in the immediate furture will be in the context of the FCC-ee running at the Z pole).
• The naming convention using the 1ss, 1c, 1cc, etc. indices for the unpolarized observables is kept, the polarized ones get indices 11-34.
• Given that almost all observables come in pairs where one is the real and the other the imaginary part (e.g. K4sc and K19). I rearranged the computation so that each combination is only computed once to avoid typos.
• Bugfix: I also found and fixed a typo in the unpolarized observables. K4s and K4sc were coded to take the imaginary parts of the given amplitude combination but it should be the real part.

[peterstangl]

Thank you! This looks good.