Validation on the fly for Settings.
Project reorganization.

1. Deleted controller SettingsController. And deleted corresponding
views (Mathes, Prices, Sectors, Stadiums)
2. Deleted all superfluous views (_Layout.cshtml, Error.cshtml)
3. Added to _SettingsLayout list-group from deleted Stadiums.cshtml
3. Changed all links on Settings/Stadiums to StadiumSetting/Index
4. Some refactoring