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.

- 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