Jupyter notebooks

What's Changed

• Add shape check to U-Net by @constantinpape in #44
• Implement block skipping in prediction by @constantinpape in #45
• Update mito-em dataset by @constantinpape in #46
• Add vnc mito loader by @constantinpape in #47
• Allow logger to generate a (run) id by @FynnBe in #48
• Add training notebooks by @constantinpape in #49

Full Changelog: 0.3.0...0.4.0