Allows to save the .llm of all mesh objects, and
all morphs of each as .obj (Wavefront OBJ File),
for import in, for example, blender.
You can also load .obj files, but of course they
will only affect what you see locally.
Added LLObjectList::getAvatar(LLUUID) for type-safe and quicker lookup
Added F32 overload to LLSD because using F64 needlessly is silly.
(And its lack of F32 overload caused issues with LLCachedControl<F32>)
