Extend JobBinary REST api to allow retrieval of raw data

Return job binary data as raw bytes.  This addition will allow
JobOrigin objects to refer to job binaries stored in the
savanna database by URL without special cases.

Change-Id: Iaf1f8cd92aa4659e6b5995089bfc89104d1b5da5
Merge "Extend JobBinary REST api to allow retrieval of raw data"