Fix prev/next day link bug introduced in v0.9.2.

- processtoday() and process_previous_days() need complete
daydirs list, not just the list of days that have unprocessed
images, in order to set prev/next day links in HTML.

- Remove daydirs_with_work().
Fix missing-thumbs-and-med-res-images bug. v0.9.3

surveillance.py:
- Improve logging in crop_image() and processImage().
- Remove daydirs_with_work() and instead have processImage()
set images_to_process flag.
- Fix handling of failure to open image in processImage().
- Fix problem of missing thumbs and med-res images due to
attempting to process image while it's still being uploaded.
If cropping fails, leave image in incoming dir unless it's more than
an hour old to give it a chance to finish uploading.
- Bumped rev to v0.9.3.

TestSurveillance.py:
- Add test for new crop failure handling.