PHP multidimentional array format

This change make alpaca sends fields names as php can parce it like multidimentional arrays
As detailed explained here: 
gitana#221

src/js/Field.js

@@ -424,7 +424,7 @@
 
                     if (lastSegment)
                     {
-                        this.name = this.parent.name + "_" + lastSegment;
+                        this.name = this.parent.name + "[" + lastSegment + "]";
                         this.nameCalculated = true;
                     }
                 }