Some refactoring and a fix

Some changes to `simplebot`:

* Made formatting pep8 compliant with exception of line length;
* Removed hardcoded `obstacle` and `spawn` sets, instead they are constructed by filtering from all locations;
* Fixed `staying` adding location of an unrelated bot;
* Replaced set([...]) and set(filter(...)) with set comprehensions.

Total size change: 8133 -> 6968