remove useless upload topic direct association
identifies all uploads with the SHA1 hash of the file content
added 'uploads:backfill_shas' rake task
make sure we only do the work once
cleaned up CookedPostProcessor and improved specs
moved `has_been_uploaded` and `uploaded_regex` to the `Upload` model
created `optimized_image` model
added `create_thumbnails?` site setting

defaults to `false`
create thumbnails when needed
refactored a bit & tested thumbnails creation
annotate models
proper column naming

silly schemaless database habits are hard to kill
Merge pull request #1037 from ZogStriP/imagineering

Imagineering