Wrap numbers from lua into osgLua in a class with custom converters

[rpavlik]

Instead of loading them directly as doubles (and thus breaking methods that want floats, when really we just don't distinguish between them since everything's a double in Lua), load them in a new class that has a handmade introspection wrapper with custom converters.

This might even allow us to get rid of or at least re-structure the "is it an int?" hack we do right now.

cc: @lpberg