Delete old files

This is a rewrite. So we need to delete everything first.
Remove graphics package

It is obsolete without the example models from the old files.
Remove old server/client application scripts
Remove old tests
Add new modules

These modules contain some basic functionality for client, server and the
models. They are far from complete though.
Update readme to new approach
Test client-side model retrieval

This tests the retrieval of models sent by a fake remote server on the
client-side.
Remove superfluous line from doctest

We are not actually working with the internal model id here.
Abstract model ID

The underlying ZODB data structure is no longer visible.
Make ServerModelLoader derive its intended base
Add state updates to base model

Swizzled data can now be used to update a model's state.
Fix assertion

An `assert` statement was missing.
Add update functionality and caching to loader

The loader uses a cache for all model objects on the client-side and caches
them in a dictionary.
Implement server-side interfaces for client

The get_updates and get_model methods are now implemented including a simple
per-object and per-user authorization scheme.
Streamline readme
Change formatting of setup.cfg
Add basic server-side user management

Also some refactoring and rearranging was done on the server.
Add todo list
Extend documentation of database
Implement login method