Bishop movement: left top diagonal
Left-top movement.
Reduced duplication.
Central point test - it covers left-bottom, right-bottom direction cases.
Real generic bishop movement (according to the diagonals rule)
Comments.
Extracted utility.
Better comment.
Test for rule 3.5
3.5 When making these moves the bishop, rook or queen may not move over any intervening
    pieces.
Can capture test.
Bishop movement seems fully implemented (include capture)
Refactored to switch.
Removed unused method.
New position generation by bishop moves.
Generating new positions after bishop movement