Fix #98

No polling support at the moment, but that can wait for a future
release.
Fix #110
Fix #111
Exposure mode "verylong" is fine

Has been for a while, so we can cut out the exclusion in the test suite
Remove blackboard, whiteboard, posterize effects

They've never worked and it just breaks end-user expectations to include
them in IMAGE_EFFECTS.
Fix #117
Fix #114
Fix #96