0.4.0-beta released

0.4.0-beta was released early in hope to get feedbacks. The API shouldn't change anymore. Further the functionality of 0.4.0 is here but a lot of things are broken due some refactoring.

So as next especially fixes to the beta code base will follow.

• fix reseting links of running channels
• fix soundfont2 support
• fix painting of GUI
• fix context menu actions of AgsMachine inherited objects
• fix preferences dialog
• probably fix AgsNotation
• enhance editor
• implement seeking

final release is planed to be released in 2 weeks.