Ignore plugin.xml because it is generated.
Added test cases before refactoring. (Had to make minimal changes code to make it testable.)
Created command object for 'file get'.
Use Grails validation.
Tidy.
Tidied thumbnail creation code.
Improve handling of height and width and stop lower-casing directory names.
Add controller method to output controller - can add checking here later.
Created new thumb tag to generate an image tag rather than just a link! Allows for images to be stored outside of web/app server docroot and be subjected to proper auth checking.
Created url mapping /thumb/fileId/width/height which is used by the g:thumb tag.