Reworked relation between tomodetector and optics

Closes #116 (closed)

• TomoDetector only expose a .optic, which is a BaseOptic
  • ._user_optic_name is now deprecated, the storage of this setting is simply done with ._optic
  • .configured_optic was dropped, better to use .config["optic"] if we have to do it
• Now a change of the actual optic is propagated for other sessions (when we use daiquiri for instance)
• A test was added to check regression on user_optics

This is finally a smaller PR than what i though, i believe it will not break the actual bl configuration.