v1.1

Change log:

• add PyTorch Train and Predict nodes
• introduce gunpowder.Graph to replace gunpowder.Points
• add support for non-spatial arrays (like one-hot classification vectors)
• add Stack to create batches with multiple samples
• add Upsample
• improved logging/error messages
• guarantee availability of requested dependencies, independent of other node's requests
• several minor bugfixes