Change DQL Parser to comply with ordered collections

This is mostly from DDC-293:

Discussion in IRC had the following results:

• Snippet should be Simple DQL
• Snippet should always be appended to any existing Order By statements, thereby only affecting the emitation of the collection elemets and not any previously requested order
• If the DQL revereses the order previously this should be overwritten, very simple:

1. @orderBy("b.start_year ASC, b.end_year DESC")
2. SELECT a, b FROM a JOIN b ORDER BY b.startYear DESC
1+2 => ORDER BY b.start_year DESC, b.start_year ASC, b.end_year DESC

• In Parser::Join() - Detect ordered collections that are fetch joined and save this information in _queryComponents.
• In Parser::SelectStatement() - If there exists a query component that has to be ordered, make sure the OrderByClause is created and append the OrderByItems from _queryComponents.
• In SqlWalker::walkOrderByClause the Order By SQL is generated correctly then.