Also draw spawn nodes
Refactor: moved cornering case to PacmanState

It only applies to pacman, but ghosts don't ever enter wall tiles so it
doesn't change behaviour of the app
Fix: Test supplied incorrect actions

It did not check for new actions each round
Refactor: Added GameState::ate_energizer

rather than encoding this in vulnerable_ticks_left
Fix: fruit would keep spawning while food_count == 70

It now spawns the tick after 70 or 170 food is eaten and food_count
changed
Refactor: Added spec notes about fruit
Refactor: Removed unused things from BckgrObj
Fix: objEl was used as if it was 1-based
Refactor: Removed unused BackgrObj::objcounter
Refactor: removed unused BckgrObj::Draw methods
Draw fruit
Refactor: always draw everything at max alpha
Can collide with fruit, and eat it
Refactor: extracted Nodes::eliminate(x,y) method
Added --hide-food
Removed redundant pacman nodes
Eliminate redundant ghost nodes
Display spawn nodes green instead of blue
Draw nodes larger and centered
Added rule that disallows reversing

Not while moving from node to node,
nor may you return to your origin when arriving at your destination node