[WIP] TreeBrowserBundle refactoring

This PR refactors the TreeBrowserBundle to make it more generic. All parameters needed to control the javascript tree are taken from the tree. As a side effect, this will (hopefully) properly implement, moving and reordering of nodes, allow for custom icons and valid_children.

Once merged there can be many different trees in the application and we can easily build a pure phpcr browser (or you could build a server side filesystem browser, which is my refactoring test case ...).

This is work in progress, especially the PhpcrOdmTree is not adapted to that yet.
additional check for route being set
adjust select.js and use JsonResponse
fix tests and integrate tree-bundle
include proper css and allow to cancel operation via event
Merge pull request #17 from uwej711/tree_refactoring

TreeBrowserBundle refactoring
remove unwanted state from tree
Merge pull request #18 from uwej711/fix-tree

remove unwanted state from tree
on create we pass the parent as parent not as id
Merge pull request #19 from uwej711/fix-parent

on create we pass the parent as parent not as id
improve doc of TreeInterface move operation. fix #22
Update Resources/public/js/select.js

Added a change trigger when updating the output field.
Can be useful if you would like to use the field in javascript. 

In my case I want to watch the field for changes, to generate a route based on the title and the parent node and set that in a custom field.
Merge pull request #26 from wjzijderveld/patch-1

Update Resources/public/js/select.js
use overlay options
Merge pull request #27 from symfony-cmf/overlay_creating_and_editing

Allow creating/editing of tree content in an overlay
test all currently supported symfony2 versions
Merge pull request #28 from symfony-cmf/travis_tweaks

test all symfony2 verions