Merge branch 'power-ups'
Merge branch 'master' into more-configuration
moved the floor setup into the configurations, made walls explicitly specify whether they're visible

Prior to this change, only moving walls were shown.
cleaned up some pointer/reference things
fixed bug with stop heading values
adding round 3
added more to round 3
specify brick size individually rather than having all bricks in a round be the same size
simplified object spec construction a bit
removed the unused json config file
Merge branch 'more-configuration'
Merge branch 'master' into power-ups
implemented laser ball power up

see #27, #44
This includes support for ball modifiers that queue up for a player and
apply to the next ball that they hit.