Simplify declare function in scripts

Using declare function is made easier by accept a single path and returning
a promise to read parameter attributes.

lib/cache.coffee

@@ -167,7 +167,7 @@ refresh = (callback) ->
         for r in res
           provisions[r._id] = {}
           provisions[r._id].md5 = crypto.createHash('md5').update(r.script).digest('hex')
-          provisions[r._id].script = new vm.Script(r.script, {filename: r._id, timeout: 50})
+          provisions[r._id].script = new vm.Script("\"use strict\";(function(){\n#{r.script}\n})();", {filename: r._id, lineOffset: 1, timeout: 50})
 
         if -- counter == 0
           computeHash()
@@ -188,7 +188,7 @@ refresh = (callback) ->
         for r in res
           virtualParameters[r._id] = {}
           virtualParameters[r._id].md5 = crypto.createHash('md5').update(r.script).digest('hex')
-          virtualParameters[r._id].script = new vm.Script(r.script, {filename: r._id, timeout: 50})
+          virtualParameters[r._id].script = new vm.Script("\"use strict\";(function(){\n#{r.script}\n})();", {filename: r._id, lineOffset: 1, timeout: 50})
 
         if -- counter == 0
           computeHash()