A MagmaDictionary is just like a regular Dictionary except that it can be very large. It is almost as fast as a MagmaPreallocatedDictionary but does not require the large disk space footprint - it only consumes as much space as needed for the objects themselves.
Also, unlike its pre-allocated brother, a standard MagmaDictionary can enumerate its elements (although, if it is large, it could take a long time).
