Minor efficiency improvements plus a synchronization fix in server example.

[wmiaw]

Select changes pulled from @quidryan's pull request #239.

• Change JavaUrl inner classes to static inner classes.
• Use EntrySet in MslObject for more efficient map iteration.
• Use Integer.parseInt() instead of Integer.valueOf() in example CLI to avoid unnecessary boxing/unboxing.
• Use ConcurrentHashMap.putIfAbsent() for synchronization safety in example server.