Code: basic puzzle board

[pv33]

Code stubs for board class are done.

• [x] Complete the code.
• [x] Update the documentation. Especially param[in/out].
• [x] Flesh out the documented test script ``puzzle/testing/basic01_board.py

[pv33]

Make sure to organize test script into distinct code sections that are enumerated and retain the English of what is going on.