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

Zframework/urlEncode.lua

@@ -1,14 +0,0 @@
-local rshift=bit.rshift
-local b16={[0]="0","1","2","3","4","5","6","7","8","9","a","b","c","d","e","f"}
-return function(str)
-	local out=""
-	for i=1,#str do
-		if str:sub(i,i):match("[a-zA-Z0-9]")then
-			out=out..str:sub(i,i)
-		else
-			local b=str:byte(i)
-			out=out.."%"..b16[rshift(b,4)]..b16[b%16]
-		end
-	end
-	return out
-end