Merge changes from the apdiocyte challenge

[BenjaminMidtvedt]

Includes changes made to deeptrack during the apidocyte challenge

Updates

• Implemented PadToMultiplesOf
• Implemented Bind and BindResolve which creates a wrapper feature that resolves a feature with a specific property
• Implemented BindUpdate which does the same, but for the update call
• Implemented AsType which casts an image to another type
• Made Crop more versatile, allowing for more ways to set the corner
• LoadImage can now receive a list of paths and will concatenate them along the last dimension
• CGan now trains using keras built in methods

Bugfixes

• Passing keras-activation functions to layer-blocks no-longer prevents the model from being loaded.

Misc

• Slightly optimized data-transfer, lessening the number of allocations. Still more to be done.
• Formated code according to pep standard.