refs #8614 spectra_list property for reduction

and unit test for this property.

Added new property which contains list of the monitors to copy to detectors in event mode. Testes assignment for this property
refs #8614 renamed copy_specta_to_monitors property

to spectra_to_monitors_list  -- hope it is more vocal and does not interfere with copy_spectra2monitors function
refs #8614 looks like all working fine

need to run system tests and add system test for this kind of workflow.