Revert "Renamed lump to merge, because lump is a terrible name"

This reverts commit 2642d7b7fee50586c68676c6d956524c547300b1.

Conflicts:
	app/helpers/admin/nomenclature_changes_helper.rb
	app/models/nomenclature_change/lump/reassignment_processor.rb
	app/models/nomenclature_change/lump/reassignment_summarizer.rb
	app/models/nomenclature_change/merge/reassignment_summarizer.rb
	app/models/nomenclature_change/reassignment_summarizer.rb
	app/views/admin/nomenclature_changes/lump/inputs.html.erb