One pull request per challenge

Please note that every submission to every challenge should have it's own pull request or in other words, one pull request per challenge. As each challenge has a limited number of rewards and we use the first-come-first-serve principle, we need to see the time stamps of each single challenge submission.

In other words,
one pull request for each challenge (Ci) , where C = {B, ID, T, EI} and i = {1,2,...}, i.e.
one pull request for challenge (B1),
one pull request for challenge (B2),
...
one pull request for challenge (X17).

The wording might not have been crystal clear everywhere in the descriptions, so we have tried to smoothened that out by now.