Pull Requests on Tasks Completion

We (@raindev and @kramar42) have a proposal to perform pull requests to initial repository on tasks completion, what will have many advantages:
 * simplify and motivate cross code review, increase collaboration by making reading, comparison and discussion of each other's code much more convenient
 * provide an ability to gain experience with Git, forks and merges for those who have no enough yet
 * make more easier for teachers to check and review our tasks in a single repository, instead of 19
 * last, but not least, our commits will be counted in GitHub contribution stats :smile:

Everyone's task could be pushed to separate directory. Five different kinds of tasks grouped in separate folders too. Proposed repository structure already created in the pull request. @raindev's and @kramar42's tasks added to illustrate  intended repository structure.
Thanks!