Select minimum or maximum value of a field in a collection.

[tuurke63]

tgoMongoCollection.FindOne() lacks something very basic, which is the possibility to find just one document having the minimum or maximum value of a field, similar to SQL SELECT MAX(). Sure it's possible to do achieve this using FIND() but this will open a large cursor on the server which eats resources unnecessarily.

I've created a merge request which adds this feature to tgoMongoCollection.FindOne().