Property definitions

nitc $ BashCompletion :: extract_options_names
	private fun extract_options_names: Array[String] do
		var names = new Array[String]
		for option in toolcontext.option_context.options do
			for name in option.names do
				if name.has_prefix("--") then names.add name
			end
		end
		return names
	end
src/toolcontext.nit:660,2--668,4