Depositor-reported cross-linking satisfaction rates

[aozalevsky]

We already have fields or tables for depositors to report EM3D, EM2D, and SAS fits values (basically, validation metrics) on a per-model basis:

_ihm_3dem_restraint.cross_correlation_coefficient field

_ihm_sas_restraint.chi_value field

_ihm_2dem_class_average_fitting table

It would be nice to have one for crosslinking data too.

Something like

_ihm_cross_link_fitting.id
_ihm_cross_link_fitting.restraint_id
_ihm_cross_link_fitting.satisfied (true/false)
_ihm_cross_link_fitting.probability (optional)
_ihm_cross_link_fitting.description

This will allow the depositors to submit their own metrics. This can be useful in cases when, for instance, depositors used different thresholds for modeling and validation (Andrea did this at least once and it's not that uncommon) or if they use a probabilistic model, that we can't directly capture/convert with simple distance-based thresholds.