[references] Add slack logging & fix clearml integration

[felixdittrich92]

🚀 The feature

• Add option to use slack for logging with tqdm in each training script

• The logs should be clear distinguishable if you log multible runs at onces to the same channel

• Slack

• ClearML

• (Optional): It would be great to track / log the learning rate also after each epoch :)

[odulcy-mindee]

I'd be a little disappointed to remove the ClearML integration because I think it's a very good tool, but unfortunately there's a memory leak that's very hard to find. For the moment, we can remove this integration but I'd like to see it added again, I think it's a very good feature.

[odulcy-mindee]

For the slack logging, I already built something internally. As discussed, there are also other tools available, it should easy to integrate that.

[felixdittrich92]

Sounds good to me then let us split this ticket into two parts one for slack and the other for ClearML 👍