core: Cleanup

Follow up on bdcfa7a5d97562708e23cdbd565361d16ac8224d
core: Allow to cycle through all possible block states
core: Get rid of sub-block c'tors and default attributes
core: Define all possible states of blocks
core: Remove redundant __str__ methods

Today I discovered vars() (-:
game: Fix the initial debugging level

Block c'tors take no arguments anymore