Adding dashboard

[mkaranasou]

This PR adds the baskerville dashboard - for feedback purposes.

Known issues:

• Ideally we should add a let's encrypt cert for all of the dashboard urls
• It takes a lot of time to build the dashboard service.
• @mazhurin I have added the feedback config and the feedback pipeline, but a new image of baskerville needs to be built after Dashboard changes pt2 baskerville#96 is merged. Let me know if anything does not work.
• Try Baskerville functionality:
  For some reason, try baskerville may fail (randomly) after some time with EOFError - I could not debug it unfortunately and it was not replicable on a local environment. It could have to do with the allocated resources for the specific container.

d_1                           | ----------------------------------------
d_1                           | Exception happened during processing of request from ('127.0.0.1', 43516)
d_1                           | Traceback (most recent call last):
d_1                           |   File "/usr/local/lib/python3.6/socketserver.py", line 320, in _handle_request_noblock
d_1                           |     self.process_request(request, client_address)
d_1                           |   File "/usr/local/lib/python3.6/socketserver.py", line 351, in process_request
d_1                           |     self.finish_request(request, client_address)
d_1                           |   File "/usr/local/lib/python3.6/socketserver.py", line 364, in finish_request
d_1                           |     self.RequestHandlerClass(request, client_address, self)
d_1                           |   File "/usr/local/lib/python3.6/socketserver.py", line 724, in __init__
d_1                           |     self.handle()
d_1                           |   File "/usr/local/lib/python3.6/site-packages/pyspark/accumulators.py", line 269, in handle
d_1                           |     poll(accum_updates)
d_1                           |   File "/usr/local/lib/python3.6/site-packages/pyspark/accumulators.py", line 241, in poll
d_1                           |     if func():
d_1                           |   File "/usr/local/lib/python3.6/site-packages/pyspark/accumulators.py", line 245, in accum_updates
d_1                           |     num_updates = read_int(self.rfile)
d_1                           |   File "/usr/local/lib/python3.6/site-packages/pyspark/serializers.py", line 724, in read_int
d_1                           |     raise EOFError
d_1                           | EOFError
d_1                           | ----------------------------------------
d_1                           | ERROR:root:Exception while sending command.
d_1                           | Traceback (most recent call last):
d_1                           |   File "/usr/local/lib/python3.6/site-packages/py4j/java_gateway.py", line 1159, in send_command
d_1                           |     raise Py4JNetworkError("Answer from Java side is empty")
d_1                           | py4j.protocol.Py4JNetworkError: Answer from Java side is empty

• Web Sockets: I am using nginx for the websocket part, but even though I can see the socket messages in the console and the connection is supposed to be established, they won't display in the client ui. Again not replicable in a local environment. It also exhibits the same behavior even if I use http://127.0.0.1:5000 as the socket url. I initially started with a separate service for the backend and the frontend but I couldn't make the socket networking work properly, so at the end I opted out for a multistage Dockerfile to minimize (the notorious Docker-related) networking issues.