Overhaul UI: Instrument view: add a checkbox for the user to be able to enable and disable the analyzer & polarizer panel

With this MR the user can use a checkbox to signal whether the instrument has both polarizer and analyzer or none of them. Up to until now, to signal that a polarizers or analyzer was nonexistent, the orientation was set to the null vector.

Furthermore a small bugfix is included to make sure that an instrument is selected after a project has been loaded.