Deprecate methods on QueryResults. add new ones

[evanchooly]

Deprecate:

1. asKeyList(*)
2. asList(*)
3. fetch(*)
4. fetchEmptyEntities(*)
5. fetchKeys(*)
6. get(*)
7. getKey(*)

Add:

1. find(*)
2. keys(*)

The new methods will return a MongoCursor as defined in the Java driver. The deprecated methods will have notations use find()/keys() as appropriate. There is a fair bit of ambiguity as to which method (fetch() vs asList()) to call. This change removes the ambiguity as there is only one method to call. This change also serves to simplify the API through the use of the driver options that can be passed in to the find() and keys() methods. This should reduce API fatigue/confusion for users and simplify maintenance in the long run.