Move forests from nodes on shutdown

* Added movedAllForestsFromNode(MarkLogicNode) to Forests interface
* Rearranged much of ForestsImpl to use MarkLogicNode instances rather
  than looking up String hostnames wherever possible.
* MarkLogicNodeImpl uses impl with node instance to avoid error of
  member not found when trying to unmount forests.
Merge pull request #53 from cloudsoft/fix/move-forests-from-node-on-shutdown

Move forests from nodes on shutdown