WIP Reworking attachment handling

Round in a couple circles but getting there...
Get unit tests green again
Base uploader gets access to relative file path

This allows all models that mount uploaders to have access to the
relative store path of their files.
Handle thunmbnails
Tidy up upload access integration tests
Whitehall.clean_uploads_root is a better name
Move config out of CarrierWave and into Whitehall

Now both incoming and clean are configured in the same place and the
configuration is not coupled to carrierwave itself.
Remove unnecessary expand_path call from helper
Correct typo
test-quarantine is no longer used
Use a proper file lock for quarantine testing
Update test cleanup task to reflect new behaviour
Add addtional signposting of monkey-patch
Rake task to fake virus scan in development

Simply copies all incoming files to the clean folder, which is good
enough to simulate a successful virus scan.