Initial implementation of MetaPlayer.
Merge branch 'master' into rulebook
Init player from definition.
Allow LuaMergeTables to work on specific indices.
Add RegistryRef.

This is to encapsulate the common operations of dealing with registry
references.
Use RegistryRef.
Fix heading comment.
Add conversion to bool.
Initial loading of wrappers.
Don't update the factories until the end.
Return nullptr if no factory has been set.
Rename "facs" to "metas".

Still not particularly descriptive, but matches the terminology we're
using in HoverScript (MetaPlayer, MetaSession, etc.).
The WrapperFactory can be const when called.
Provide access to the meta constructors.
Ignore C4297 warning in Luabind.
Fix swapped inside/outside classes.
Specify smart pointer policy for MetaPlayer.

This fixes the object_cast when we get an instance of a Lua subclass.
Fix operator() compilation and add logging.
Handle on_init in MetaPlayer.
Add wrapped PlayerPeer as a property.