move apis into rom/modules/main for shell compatibility

builder/viewer.lua

@@ -1,7 +1,7 @@
 local Builder   = require('builder.builder')
 local Schematic = require('builder.schematic')
 local TableDB   = require('core.tableDB')
-local Util      = require('util')
+local Util      = require('opus.util')
 
 local device    = _G.device
 local fs        = _G.fs
@@ -157,4 +157,4 @@ for i = 1, #Builder.schematic.blocks do
 end
 
 pcall(_G.read)
-cn.clear()
+cn.clear()