Decide on a way to test movegen, among other functionality

Parsing is slow is one of the reason originally to go with
piece position test data collections. However, it is complicated
to show clearly what data is in each collection. The board string
has the advantage of making it very clear and straightforward
where to place the pieces. Also, any number of blocker pieces
can be placed on the board. The method is even flexible enough
to support testing of more complex positions than simple 'unit'
positions.

Parsing performance needs to be improved to make this usable.