When dragging and dropping nodes in trees, don't touch the lock version of affected records.

This prevents problems when the user has an edit form open, manipulates the
tree, then submits the form.
WIP make position sticky after move (when form is open)
Update the tree.js to update the position of the selected node when nodes are moved (to ensure it's hidden input value for position is kept up to date)
Rejig orderable
Merge pull request #433 from hudmol/tree-change-locking

When dragging and dropping nodes in trees, don't touch the lock version ...