[Feature] Learner upload.

[sebffischer]

To be able to upload resample results to OpenML we need to get a repr for the learners. This is problematic in two cases:

• GraphLearner - here it is somewhat tricky to obtain a representation
• Learners with constructor arguments.

temporary (non ideal) solution:

• If repr does not exist, the user has to manually provide the setup string.

Another thing that is problematic:

• It is not straightforward to obtain hashes that uniquely identify graph learners.

[sebffischer]

wont do this