RENAME: components.voigt.Voigt.origin -> Voigt.centre
BUG-FIX: in EELSSpectrum the global elements variable was being overwritten in the add_elements method. Bug reported by Magnus Nord in issue #58
BUG-FIX: get_fine_structure_as_spectrum in eels_cl_edge component
BUG FIX: model.smart_fit() with component with free_energy_shift raised
an error
BUG-FIX: fixes #59
BUG-FIX: when a parameter was twinned its connected functions were not being honoured by its twin
Merge branch 'master' into model_adjust_centre
BUG-FIX: the adjust_position was also adding a position widget when the parameter was twinned