ZioAttributeGUI.py: remove useless class import

Signed-off-by: Federico Vaga <federico.vaga@gmail.com>
gitignore: ignore __pycache__ directory

Signed-off-by: Federico Vaga <federico.vaga@gmail.com>
zgui: use PyZIO v0.5a that export ZioUtil

Signed-off-by: Federico Vaga <federico.vaga@gmail.com>