feed data bytes to VIC-II sprites.
accept sprite pixel data from VIC-IV and prepare for use.
fix sprite_datavalid computation.
fix an assortment of sprite rendering bugs.
remove some debug output.
fix bugs in receiving sprite data  bytes from VIC-IV
try to flatten logic a little.
substantially flatten logic for sprite data fetching
put some default data in for a sprite.
fix sprite pixel data pipeline bug
sprite data for testing.
remove debugging