Add settingtypes.txt for Minetest Game

Commit originally by PilzAdam.
Settings appear in advanced settings menu.

settingtypes.txt

+# This file contains settings of minetest_game that can be changed in
+# minetest.conf
+
+#    In creative mode players are able to dig all kind of blocks nearly
+#    instantly, and have access to unlimited resources.
+#    Some of the functionality is only available if this setting is present
+#    at startup.
+creative_mode (Creative mode) bool false
+
+#    Flammable nodes will be ignited by nearby igniters. Spreading fire may
+#    cause severe destruction.
+#    Spreading fire nodes will disappear when fire is disabled, but
+#    'permanent_flame' nodes are unaffected.
+enable_fire (Fire) bool true
+
+#    If enabled, steel tools, torches and cobblestone will be given to new
+#    players.
+give_initial_stuff (Give initial items) bool false
+
+#    If enabled, players respawn at the bed they last lay on instead of normal
+#    spawn.
+#    This setting is only read at startup.
+enable_bed_respawn (Respawn at bed) bool true
+
+#    If enabled, the night can be skipped if more than half of the players are
+#    in beds.
+enable_bed_night_skip (Skip night when sleeping) bool true
+
+#    When TNT explodes, it destroys nearby nodes and damages nearby players.
+#    This setting is disabled by default on servers.
+enable_tnt (TNT) bool true
+
+#    The radius in which nodes will be destroyed by a TNT explosion.
+tnt_radius (TNT radius) int 3 0
+
+#    The time in seconds after which the bones of a dead player can be looted
+#    by everyone.
+#    Setting this to 0 will disable sharing of bones completely.
+share_bones_time (Bone share time) int 1200 0
+
+#    Replaces old stairs with new ones. Only required for older worlds.
+enable_stairs_replace_abm (Replace old stairs) bool false