updated NestedSet to use Zend coding standards.  still a few problems with return values using () that need to be looked at.

joesimms: initial draft for tree support. NestedSet support included, placeholders for other popular implementations also included. Read the README.tree file for more information and changelog to core files. Modified core files have also been included in this commit. hope it works and you like it !

- Lazy connections possible through Doctrine_Manager::addDSN($dsn, $connectionName). Connections will then be opened automatically when they are requested the first time.

Changes concerning multiple connection control:
- injection of the Connection object into the Doctrine_Table constructor, instead of a static lookup.
- added optional Connection parameter to save/delete of Doctrine_Record and Doctrine_Collection