This solver is able to take definition in yaml format. For now it supports
kana in this form:

- normal
- frozen
- rock
- void
- empty


Level files are store in `levels`. Format is yaml.
Example file `level_XX.XX.yaml`::

    # kana quest grid level XX.XX
    size: [3, 2]
    max_actions: 1
    target_score: 3
    grid: [
      [void, null], [myst, nu  ], [void, null],
      [froz, ne  ], [empt, null], [rock, 'no'],
    ]


**WARNING** in level file definition:
The kana 'no' need to be protected else the program convert it into False...


Run::

    ./solver.py kana_quest_level/level_4.6.yaml
    ./solver.py -p kana_quest_level/level_4.6.yaml
    ./solver.py --print kana_quest_level/level_4.6.yaml
    ./solver.py -h