[Dependencies] Add rapidjson 0.11
Prettifying again
[Data] Add a function to serialize a Describable into a JSON string
[Data] Add a function to serialize a Describable into a rapidjson object
[Data] Add a function to deserialize a Variant from a rapidjson value
[Data] Add a function to deserialize a Describable object from a rapidjson value
[Data] Add a function to deserialize a Describable object from a JSON string
[Dependencies] Update rapidjson to get rid of an annoying warning when using GCC