Change the instrument schema to make the list of collimators a part of detector objects

[TimofeiZavileiskii]

Change the instrument schema to instead of having a list of collimators as a part of the instrument, make it part of a detector object.

Right now the collimator has the detector it is attached to as a string inside it, allowing to have collimators with the same name if they are attached to different detectors. It would be more logical if instead collimators would be a part of the detector object they are attached to like links and joints are a part of the positioner object.

It would require:

• Update how the Json files are processed into an instrument
• Implement backwards compatibility to be able to read and convert files of old schema into the new one
• Update documentation about the Instrument Schema