Improve json/c++ name-mapping

[jgaa]

The current implementation works only on the root-level of the serialization. We need to map the mapping to a class, so that it works also for recursive properties.

One potential implementation is to use traits, where the mapping is pinned to a class at compile-time trough templates. Another option is to make the mapping configurable during runtime, by assigning it to classid's, and provide a list of such mappings to the serializer.

[CrazyKidJack]

I just wanted to say that this is the biggest feature request I have. Most APIs don't return ONLY the data you want. There are usually some meta-data fields in the response as well and it often is nested in several levels.