Add leaderboard and leaderboard box. Restyle right-side box.
Change vote counting mechanism so that only non-skipped frames are counted towards vote totals. Also increment "skips" column when a frame is skipped.
Change SELECT statement so that images that have been skipped are not shown again. Also change to prefer images that have not been voted on (thought this was already done...)
Merge branch 'leaderboard'

Conflicts:
	submit.php - due to commit 1d47a6 - manually fixed