Better support for twins

[dkratzert]

• Description of twinning
• Test more types of twins
• Add twin matrix to the structure report.
• What else?

[dkratzert]

https://www.iucr.org/__data/iucr/cifdic_html/1/cif_twinning.dic/Ctwin.html

I should add a twin editor similar to the author editor. Not sure if I handle all cases or the most common.

FinalCif should at least collect the twin matrix information from SAINT and add a loop:
loop_
_twin_individual_id
_twin_individual_mass_fraction_refined
_oxdiff_twin_reflns_isolated
_oxdiff_twin_reflns_overlapped
_twin_individual_twin_lattice_type
_twin_individual_twin_matrix_11
_twin_individual_twin_matrix_12
_twin_individual_twin_matrix_13
_twin_individual_twin_matrix_21
_twin_individual_twin_matrix_22
_twin_individual_twin_matrix_23
_twin_individual_twin_matrix_31
_twin_individual_twin_matrix_32
_twin_individual_twin_matrix_33