Change Exception throwing

• Change ValidationException
• Remove custom MongoDBException

Add $orderby option for relationships / references

• in url example : a_node.orderby(a_field)
• in field example : { "$orderby" : "a_field" }

Change Validation process

• Remove callback from all functions
• Return null if validationRule is validated
• Return a ValidationException if validationRule is not validated

Fix some mongodb lib changes

Version 0.2.0

Major changes :

1. Change all delete words into remove

Examples :
- delete() -> remove()
- deleteSomething() -> removeSomething()
- isDeleted -> isRemoved
- ...

Slight changes :

1. Throw Error objects instead of strings

Exemples :
- throw "an error"; -> throw new Error("an error");