Have to_array() work like in the DB class

[fuel]

Have to_array() work like in the DB class

[jschreuder]

This may be implemented with to_array() by having it accept an array of values that are the only ones returned (or removing some by using array('field' => false)).
Another way this could be implemented would be by creating a post-to_array event which gets passed the new array to allow you to change it with an observer before it's output.

But as discussed on IRC: hydration will never ignore anything that was fetched from the DB, that's just dumb & wastefull - if you're going to ignore a value during hydration it shouldn't have been fetched in the first place. (Relates to issue #17)

[jschreuder]

Thought longer about this and decided to nix the whole idea. Doesn't really do much usefull, and when selecting only specific fields is possible in the next version this won't be necessary anymore.