Use a new game screen or move new game settings to the app menu

Submitted by Robert Ancell @robert.ancell

Link to original bug (#664977)

Description

Use a new game screen that shows the game options at the start of a game. This means that preferences dialogs for game difficulty can be removed and resolves the issue that options can be changed while a game is in progress. See the Sudoku start screen for ideas.

Version: git master