Add support for default Mongo operators in EMongoCriteria ('$gt')

[thaddeusmt]

If you pass in a configuration array of 'conditions' into the EMongoCriteria, it will error if you use a default operator like '$gt'. It is happy to translate the '>' operator to the Mongo one using the $operators array in EMongoCriteria, but it does not allow using the actual '$gt' operator. Should be an easy fix and allow folks already familiar with Mongo queries to more easily use this (great!) extension, without learning the operator alias ('greater' and '>').

Thanks