整理代码，新增string扩展模块，把一些小模块合并进string和table扩展模块中

parts/modes/sprint_20l.lua

@@ -16,7 +16,7 @@ return{
 		PLY.draw.drawTargetLine(P,r)
 	end,
 	score=function(P)return{P.stat.time,P.stat.piece}end,
-	scoreDisp=function(D)return TIMESTR(D[1]).."   "..D[2].." Pieces"end,
+	scoreDisp=function(D)return STRING.time(D[1]).."   "..D[2].." Pieces"end,
 	comp=function(a,b)return a[1]<b[1]or a[1]==b[1]and a[2]<b[2]end,
 	getRank=function(P)
 		if P.stat.row<20 then return end