Enhanced API and added a spec for ORMultiMap

In addition the removeBindings api call has been removed in favour of using the newly introduced get, put and remove map level operations.
do we need to expose the `ORSet` of the values at all? What is the purpose of this method?
could it be `value: Set[Any]` and then an `ORSet` with those values will be created internally.
`entries` would return `Map[String, Set[Any]]`