allow for implementation flexibility storing and retrieving files
Modified Image list inflate to properly expand a list of files.

- File.load only returns one file object, not an array as this code assumes.
- Added code to parellelize file loading, and return the sorted list to the original callback when complete.
Added Files.all for retrieval of multiple files by array of ids
- Simplified image_list inflate(), replacing parallel loading of image files with Files.all call
minor refactor of File.all yield call
Merge branch 'master' into feature/file-storage
tweak rock config to point to example basic server