Changes to the object linking and naming
- Moved back to list based, rather than dict based, so that object can be renamed without having to rename all the dictionaries.
- Also added delete_object method which roots the object out of the linking tree, so it effectively doesn't exist, although it's still available on the command line
- Geometry objects can't be renamed, same type of objects can't have same name
Added documentation to the find_object and delete_object methods