v0.6.0

This release improves the behavior of the prelude

The Python code in the prelude attribute of the global section is now executed raw, before any expansions are done. Expansions in the prelude are probably not very useful, as dynamic substitutions can be done easily and way more flexibly in the Python code itself. Conversely, the change means that you can now finally use names defined in the prelude in expansions in the global section, which should have many uses.