Bug: parchmint throws keyError when certain key is not detected in json

[bjoernh2000]

File "/home/ubuntu/pyparchmint/parchmint/device.py", line 228, in parse_from_json
    for layer in json["layers"]:
KeyError: 'layers'

3DuF didn't generate the 'layers' key for the JSON object, and on parsing the file into parchmint a key error is thrown.

[rkrishnasanka]

@bjoernh2000 this probably needs to extend for more cases too. Like when no connections, components, params keys are found. When printing the error, it should account for the detail where the object tree this error is coming from.