Accept ghost_name as well as inner_name to create_entity

[Therax]

Most places in the API, an entity-ghost is referred to as having a ghost_name to describe the actual entity to be built: find_entities_filtered, LuaEntity. The exception is LuaSurface::create_entity, which requires that the parameter be "inner_name".

"inner_name" needs to be retained for backwards compatibility with existing mods, but it would be nice if create_entity would also accept ghost_name for consistency with the rest of the API.

[Rseding91]

Ok. I added it for 0.17.