Start merging QQwing wrapper with libsudoku
Fix build with automake 1.13
Fix build

Obviously the solution to our linker error is to tell Automake to
compile a file that doesn't exist. This is actually the documented
solution in the Automake manual. Good God.
Make sure to distribute QQwing-wrapper.h
Change some stuff

This is a horrible commit. Never do this.

* Rename files
* Style changes
* Fix two memory leaks
Don't mix new and free()

This is undefined behavior
Create SudokuGenerator class
Code cleanup
Use QQwing for puzzle generation

At this point, only the SudokuPrinter depends on data files.
Starting a new game doesn't take a puzzle from the Store,
but requests QQwing to generate one of the selected difficulty.

Also renamed our DifficultyCategory enum values
to match with those of QQwing
Make SudokuGenerator methods static
Use QQwing for SudokuPrinter
Remove SudokuStore and the puzzle data files

- Also remove set_from_string() method from SudokuBoard
since Saver and Generator directly use insert() to fill the board
Update gschema.xml to use new difficulty enums
Display QQwing version on about dialog
Tweak the about dialog message slightly
Simplify qqwing_get_version()

C++ makes me feel like not a GNOME programmer at all.
Remove now-unused include