Player model and Leaderboards page

[UncleVasya]

• [x] Player model;
• [x] PlayerAdmin;
• [x] Leaderboards page;

• [x] Leaderboards page design;

• [x] staff accounts for ladder admins with permission to edit players;

• [ ] populate DB with real players;

• [x] integrate new functional with balancer;

[UncleVasya]

Done.

Populating DB with real data will begin on the start of next ladder season.