Update Minesweeper/GameBoard.cs
Merge branch 'master' of https://github.com/TeamSilver/Minesweeper
Update GameBoard.cs with good method names:

- PutMines ->AddMines
- proverka -> FieldInGameBoard
- InitializeBoardForDisplay -> InitGameBoard
- Display -> DisplayGameBoard
- FindMine -> IsMine
- Край -> DisplayAllFieldsInBoard
- proverka2 -> IsDisplay