Add settingtypes.txt to configure player trapping and message logging

There are also some changes to fix problems when trapping is enabled while damage is disabled or the other way round.

nether/settings.lua

@@ -0,0 +1,23 @@
+local default_settings = {
+	trap_players = true,
+	log_to_chat = false,
+	log_level = 2,
+}
+
+nether.settings = {}
+
+for name,dv in pairs(default_settings) do
+	local setting
+	local setting_name = "nether." .. name
+	if type(dv) == "boolean" then
+		setting = minetest.settings:get_bool(setting_name)
+	elseif type(dv) == "number" then
+		setting = tonumber(minetest.settings:get(setting_name))
+	else
+		error"[nether] Only boolean and number settings are available"
+	end
+	if setting == nil then
+		setting = dv
+	end
+	nether[name] = setting
+end