new __str__ for Board() thx to Jared
modify Board()__str__ so that row ref is alphabetic
testing __str__ with config module
experimenting new show_game and _filter
reorganising the modules
minor adjustment to control.play
test the merge
merge conflict fix
new __str__ for Board
show_game() show_board() defined in config used in control
 trying to debug _head2tail
Revert " trying to debug _head2tail"

This reverts commit 541ceee5e11aff924f2b201cb7d6a057507fccee.
_head2tail() debugged
some visual edit of prints in control players and config