Beam tracker

Feature a beam tracker.

The architecture/need/modelization is describe at https://confluence.esrf.fr/pages/viewpage.action?pageId=128871006

• tomo_config.beam_tracker (optional) expose the modernization of the beam
• tomo_config.tracked_translation_x (optional) expose an axis equivalent to translation_x
• tomo_config.reference_position (optional) is used by scientist to setup a reference and move back the sample stage to it

It was difficult to put that stuff at different places cause dependencies with the other components. But it works.

Here is an example of configuration

controller:
  - package: tomo.controllers.beam_tracker
    class: BeamTracker
    name: id16_beam_tracker
    plugin: generic


  - package: tomo.controllers.beam_tracker
    class: BeamTrackerCalcController
    beam_tracker: $id16_beam_tracker
    plugin: generic

    axes:
      # sample stage
      - name: $sx
        tags: real sx
      - name: $sy
        tags: real sy
      - name: $sz
        tags: real sz

      # beam tracking
      - name: sxbeam
        tags: sxbeam

- name: id16a_config
  plugin: bliss
  class: TomoConfig
  package: tomo.tomoconfig

  ...

  # Contains information from the location of the beam.
  # This is used to track the sample with the beam
  beam_tracker: $id16_beam_tracker

  # Axis with the same role as x-axis, but compensating y and z to follow
  # the beam with the sample
  tracked_translation_x: $sxbeam

  # reference for translation x/y/z that user can setup.
  reference_position: {}  # <- empty config

  ...