Add animated particle support

Also implements an ignition failure sound.

portal_api.txt

@@ -48,7 +48,9 @@ Call these functions only at load time:
     * Unregisters the portal from the engine, and deletes the entry with key
       `name` from `nether.registered_portals` and associated internal tables.
     * Returns true on success
-* register_portal_ignition_item(name)
+* register_portal_ignition_item(name, ignition_failure_sound)
+    * ignition_failure_sound is optional, it plays any time an attempt to use 
+      the item occurs if a portal is not ignited.
 
 
 
@@ -58,31 +60,45 @@ Portal definition
 Used by `nether.register_portal`.
 
     {
-		shape = PortalShape_Traditional, 
+        shape = PortalShape_Traditional, 
         -- optional. 
 
-		wormhole_node_name  = "nether:portal",
+        wormhole_node_name  = "nether:portal",
         -- optional. Allows a custom wormhole node to be specified.
         -- Useful if you want the portals to have a different post_effect_color
         -- or texture.
 
-		wormhole_node_color = 0,
+        wormhole_node_color = 0,
         -- A value from 0 to 7 corresponding to the color of pixels in 
         -- nether_portals_palette.png:
-	    --     0 traditional/magenta
-	    --     1 black
-	    --     2 blue
-	    --     3 green
-	    --     4 cyan
-	    --     5 red
-	    --     6 yellow
-	    --     7 white
+        --     0 traditional/magenta
+        --     1 black
+        --     2 blue
+        --     3 green
+        --     4 cyan
+        --     5 red
+        --     6 yellow
+        --     7 white
 
-		particle_color      = "#808",
+        particle_color      = "#808",
         -- Optional. Will default to a colour matching the wormhole_node_color
         -- if not specified.
 
-		frame_node_name     = "default:obsidian",
+        particle_texture    = "image.png",
+        -- Optional. Animation and particle scale may also be specified, e.g:
+        -- particle_texture = {
+        --      name = "nether_particle_anim1.png",
+        --      animation = {
+        --          type = "vertical_frames",
+        --          aspect_w = 7,
+        --          aspect_h = 7,
+        --          length = 1,
+        --      },
+        --      scale = 1.5
+        --  },      
+        -- See lua_api.txt for Tile Animation definition
+
+        frame_node_name     = "default:obsidian",
         -- Required. For best results, have your portal constructed of a 
         -- material nobody else is using.
 
@@ -100,7 +116,7 @@ Used by `nether.register_portal`.
         -- Required. Return true if a portal at pos is in the realm, rather 
            than the surface world.
 
-		find_realm_anchorPos = function(surface_anchorPos),
+        find_realm_anchorPos = function(surface_anchorPos),
         -- Required. Return a position in the realm that a portal created at
         -- surface_anchorPos will link to.
         -- Return an anchorPos or anchorPos, orientation
@@ -110,7 +126,7 @@ Used by `nether.register_portal`.
         -- orientation, otherwise the existing portal could be overwritten by
         -- a new one with the orientation of the surface portal.
 
-		find_surface_anchorPos = function(realm_anchorPos),
+        find_surface_anchorPos = function(realm_anchorPos),
         -- Optional. If you don't implement this then a position near the
         -- surface will be picked.
         -- Return an anchorPos or (anchorPos, orientation)
@@ -120,16 +136,16 @@ Used by `nether.register_portal`.
         -- orientation, otherwise the existing portal could be overwritten by
         -- a new one with the orientation of the realm portal.
 
-		on_run_wormhole      = function(portalDef, anochorPos, orientation),
+        on_run_wormhole      = function(portalDef, anochorPos, orientation),
         -- invoked once per second per portal
-		on_extinguish        = function(portalDef, anochorPos, orientation),
+        on_extinguish        = function(portalDef, anochorPos, orientation),
         -- invoked when a portal is extinguished, including when the portal
         -- it connected to was extinguished.
         on_player_teleported = function(portalDef, player, oldPos, newPos),
         -- invoked immediately after a player is teleported
         on_ignite            = function(portalDef, anochorPos, orientation)
         -- invoked when a player or mesecon ignites a portal
-		on_created           = function(portalDef, anochorPos, orientation)
+        on_created           = function(portalDef, anochorPos, orientation)
         -- invoked when a portal's remote twin is created, usually when a
         -- player travels through a portal for the first time.
-	}
+    }