Added 'make dist' target
Removed *.dirs

Per Debian docs, *.install files should be enough.
Added bosp.menu
Added bosp.docs
Reformating some files using templates generated by debmake

debmake --binaryspec "bosp:bin,liboskoengine0:lib,liboskoengine0-dev:dev,liboskoengine0-dbg:dbg" -j -x4
Added default maintainer scripts generated by debmake
Added libsokoengine0-dbg package.
Added correct dependencies to -dev package.
Added debian/watch from debmake generated template.
Removed CMake install(EXPORT...)

There has to be better way to export CMake package than maintaining
sokoengine-config.cmake which unmodified works only for non-multiarch
installations.
Added multiarch support to Debian package.
Override override_dh_auto_test until problems with it are resolved.
Fixing some of linthian warnings
Merge branch 'feature/improve_debian_package' into development

Refined Debian package configuration solving more issues with
Debian packaging. This is still not complete, but it is a step
forward.
Added GameBoard::resize_and_center
PuzzleEditor now works on copy of GameBoard.
Created GameBoardEditor and delegated GameBoard editing from PuzzleEditor.
Removed metadata editing from PuzzleEditor

This complicates implementation of undo stack. It would be nice to have it
here, maybe it can be returned at later stage.
Removed model changes tracking from PuzzleEditor.
Removed local QToolbar from PuzzleEditor