Define and use a common Sudoku type.

* Main.fs: Return a common Sudoku type.

* Main.fs: Define a Sudoku type.

* FsSudoku.SadMan.Tests.fsproj: Add test files to project.

* Test.fs: Fix failing test.

* fileformatexample-pencilmarks.sdk: Convert to CRLF.
Stylistic improvements.
Be more consistent with .NET naming conventions.

Fixes #1