Allow projections that complement user QueryOptions?

Can this "if" be removed?

https://github.com/opencb/datastore/blob/develop/datastore-mongodb/src/main/java/org/opencb/datastore/mongodb/MongoDBNativeQuery.java#L65

If a projection is provided by the programmer, user "options" would be ignored. By removing this if we would allow to provide a projection object which would then be complemented with the user "options" within "getProjection"
