added support for CASCADE as per CouchDB/ORM etc
ensure the collection is initialized before unwrapping
ported some tests for cascading from CouchDB ODM
cosmetic tweaks
Merge pull request #200 from doctrine/cascade_support

added support for CASCADE as per CouchDB/ORM etc
First attempt
ODM Query Builder implementation

- Follows closely the ORM QueryBuilder
Expression visitor: Comparisson
Rest of ExpressionVisitor implementation
Cleaned up QueryBuilder (a little)
Removed .swp
Fixed up QueryBuilder