Implement Exists in Proximus.DBCollection<T> properly

[soundarmoorthy]

As of now we are not able to generalize the way exists() can be implemented across different entities (Geocode, GeocodeMatrix, GeoDistance). This needs to be fixed.

• A simple suggestion would be to have Exists() as a contract in IEntity and be implemented across different entities.

• Another simple suggestion would be implementing Equals() in all entities and use the equals method as a predicate in the DBCollection.Exists() method.