Created type definitions for jquery.fancytree.

#3164

Created type definitions for jquery.fancytree. (https://github.com/mar10/fancytree).

I placed all interfaces in a module called Fancytree to avoid polluting the global namespace as suggested. However, some types in this module are also prefixed with Fancytree in their names. This is because the types are documented with those names in the Fancytree documentation (http://www.wwwendt.de/tech/fancytree/doc/jsdoc/), so I did not want to change this. Otherwise it would have been nicer to remove this prefix, so that instead of for example "Fancytree.Fancytree" or "Fancytree.FancytreeNode" we would have "Fancytree.Tree" and "Fancytree.Node". Any thoughts on this?