Alter category key pd_calib_xcoord

[rowlesmr]

pd_calib_xcoord - originally keyed on .id and .xcoord_overall_id (linked to _pd_calib_xcoord_overall.id). There was no way to link each point of the calibration to the detector it was calibrating. .xcoord_overall_id was demoted to linked non-key data item. .detector_id promoted to part of composite key. Updated the examples.

[jamesrhester]

Just making sure I understand the logic here. An x-calibration, described in PD_CALIB_XCOORD_OVERALL has a globally unique identifier which identifies a diffractogram and phase used for the calibration. As neither phase nor diffractogram are keys, multiple calibrations could be listed that use the same source diffractogram and phase but go about it slightly differently. The particular calibration used is therefore indicated in the _pd_calib_xcoord.xcoord_overall_id data name. Via this calibration measurement we have the instrument and detector that is the target of calibration, so doesn't that mean we already have the detector_id without needing to restate it? I believe a detector should never be calibrated using a measurement from a different detector?