support for getting files from disk. removed dependency on restlet.

 * removed dependency on Restlet. Now only using Apache HttpClient.
 * added support for getting files directly from disk instead of streaming through the Web API (including unit tests).
 * removed code for callbacks - callbacks has been dropped from the Web API to keep things simple, polling is efficient enough for our needs.
 * fixed "filename" and "relativeHref" variables in JobResult; the "/idx/$IDX" part is now stored in the relativeHref instead of the filename.
 * copied utils.Files from the Web UI codebase to be able to create ZIP files.
Merge branch 'get-from-disk-and-remove-restlet-dependency'

closes #1