More cunning added to puzzle generator

More cunning has been added to the puzzle generator in version 1.58.0. There is also a new setting for adjusting the size of the numbers in a puzzle. All the changes for this version in detail:

• New logic has been added to the puzzle generator, used when generating very difficult puzzles in Expert mode.
• More refinements to the way the puzzle generator estimates the difficulty of the new puzzles it generates. 
• A new setting in the section “Layout & Appearance” makes it possible to adjust the size of the numbers in a puzzle. This setting works independently of the text size that is set on the device.
• The “dimmed” appearance for dark mode is a bit darker.
• More improvements to the way the help chooses where to show a hint. Steps involving just a small change to candidate values are selected according to where there is most benefit in preparing the way for a more significant step.
• Fix for an issue where an empty square would sometimes display a dotted block outline if a clue was tapped and the row or column had errors.
• The arrow for the help is more animated.