Add new 5.1 default theme Lambda

I'd like to thank everyone who made this possible;, including but not
limited to Riakodoadm, MrThatKid, kyzentun, Luizsan, JoseVarelaP,
everyone else who provided feedback and bug reports.

Themes/default/Graphics/NoteField layers.lua

@@ -0,0 +1,22 @@
+local filter_color= color("0.135,0.135,0.135,1")
+
+local layers= {
+	Def.Quad{
+		InitCommand= function(self)
+			self:hibernate(math.huge):draworder(notefield_draw_order.board)
+				:diffuse(filter_color)
+		end,
+		PlayerStateSetCommand= function(self, param)
+			local pn= param.PlayerNumber
+			local alf= player_config:get_data(pn).ScreenFilter
+			if alf > 0 then
+				self:SetHeight(4096):diffusealpha(alf):hibernate(0)
+			end
+		end,
+		WidthSetCommand= function(self, param)
+			self:SetWidth(param.width+8)
+		end,
+	}
+}
+
+return layers