Refactor File/Disk Access for Private and Staged Images

[pwscsiro]

It might be worth considering refactoring the way this is done with a view to removing duplication by centralising the read and writes in one place, maybe in a Service supported by some object oriented components. The latter would help reduce reliance on static method calls and magic hard-coded strings. The various file paths might be good as properties on a bean. The benefits of this would be easier to read, easier to maintain, easier to change, easier to extend. The features that would be impacted include uploading images, displaying images, deleting images, creating thumbnails, creating tiles and publishing (moving) images to the central repository - Biocache.

[ben3000]

See also #322.