reverting the reorganization done in 3455-3456 in order to make merging my experimental branch to trunk easier.

Preparation for new organization of code in to sub packages. Changed autoload() to work with new structure.

Fixed an issue with the NestedSet where the baseAlias was not reset properly under some circumstances.

Added copy() method to Query.php and made NestedSet.php use it because native clone() does not work. Also Added ->getSql() to getRootAlias() so that _aliasMap is present after the parsing.

- Removed the reserved alias "base" from the nested set. It's no longer necessary to use that. Use whatever alias you want.

Improvements and enhancements to the NestedSet (not BC! please have a look at draft/nestedset_changes.tree).
Added a model that was missing in the repos (model/BlogTag).
Updated a testcase.

Ticket: 328

joesimms: added support for many roots for one table, added another example illustrating this, see EXAMPLE2.tree.php, also changed toString to __toString in getPath()

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 !