feat(problems): solved/unsolved filtering

Signed-off-by: A. Prooks <aprooks@live.ru>
test(ProblemsList): problems can be preloaded

Signed-off-by: A. Prooks <aprooks@live.ru>
chore: built projects

Signed-off-by: A. Prooks <aprooks@live.ru>
Merge pull request #41 from aprooks/feature/unsolvedProblems

(un)solved problems