Added better support for EELS data
- Added EELS search filters into the GUI (resolution, energy_window, detector_type, eels spectrum)
- Fixed issue in parser not reporting units for energies
- Updated the experimental metainfo for device settings to include units and small description.
- Added new EELS metadata into results together with regtests
- Small GUI refactoring for the process of serializing/deserializing filter values (was needed for serializing energy_window which does not correspond to a single metainfo quantity)
- Small GUI refactoring for the components used to display properties in the overview (