WFCORE-14 - add operations for manipulating list & map attributes

initial version, i want do do some more cleanup of apis for easier manipulating on side of write/read attribute handlers
A `LinkedList` will use `Collection.toArray()` then create a new `LinkedList.Node` for each entry in the list. An `ArrayList` just copies the array with `Collection.toArray()`. Anyway, probably not a big deal. :)