Removed redundant rules (clauses) from the solver.
Introduced a configurable parameter N so that the solver code can be
applied for larger (i.e., 16x16 or 25x25) puzzles easily.
The previous commit that replaced hard-coded constants with symbolic
constants in PuzzleSolver was incomplete.

I considered that NN is a better name than M for a constant
to mean N*N.
Corrected some comments in OpenCVInitializer
Removed codes to show a _debug image_ during puzzle capture.
The feature was used in an early stage of development,
and it has not been for a long time,
but the related codes were still around.
Merge branch 'solver'
Changing the directory structure of the repository.