Need to be able to fix parameters

[drummerJim]

As a member of beamline staff I want to be able to edit the input parameters. For example, wavelength, beam centre, detector distance. I would also like to have the option of fixing these parameters. This helps to diagnose issues with the beamline. This is also useful if the header information is incorrect.

[dagewa]

Currently the header information can be overridden during the dials.import step, but it would certainly be useful to have easy access to experimental geometry at any point by making the model states shown in DUI editable.

We discussed this in the DUI meeting and decided that such changes should cause a run of a command that edits the relevant .json file. This action should cause a new node to appear in the history so that the user can select the state before or after the change.

It turns out the command already exists, dials.modify_geometry :-)

[dagewa]

BTW parameters can be fixed during indexing and refinement, but this requires use of the advanced input tab at the moment