disable castling and en-passant moves

There are some bugs triggered by moves with more than source and
destination fields - castling, en-passant and promotion. I disable them
until the rest of the code is correct.

Signed-off-by: Cristian Stoica <crististm@gmail.com>
add board positions that triggered bugs

Signed-off-by: Cristian Stoica <crististm@gmail.com>
move engine code in a separate file

Signed-off-by: Cristian Stoica <crististm@gmail.com>
make the board nicer

Signed-off-by: Cristian Stoica <crististm@gmail.com>
add experimental code for user moves

Signed-off-by: Cristian Stoica <crististm@gmail.com>
playing with king moves

Signed-off-by: Cristian Stoica <crististm@gmail.com>
stash experimental code

Signed-off-by: Cristian Stoica <crististm@gmail.com>