Let team captains choose side and pick order.

[UncleVasya]

• [x] !sidepick command that:
  • [x] determines captains;
  • [ ] makes a list of available choices: !fp !sp !radiant !dire;
  • [x] randomly chooses a captain to pick first;
  • [x] can be used only once per queue;
• [x] !fp !sp !radiant !dire commands:
  • [x] let only captains use it;
  • [x] check that captain uses it on their turn;
  • [x] remove corresponding options from the list of choices;
  • [ ] when choosing side, flip lobby teams if needed;
• [x] when starting the game, set lobby first pick to corresponding captain's team;