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 !

Total rewrite for DQL alias model: now using short aliases instead of long aliases (needed for Oracle portability). 

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