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

--no commit message