Add request timeout and fallback retries to FileDownload utility class.
Add request timeout and fallback retries to FileDownload utility class.

jayoshih/kolibri,indirectlylit/kolibri,jayoshih/kolibri,learningequality/kolibri,DXCanas/kolibri,jonboiser/kolibri,christianmemije/kolibri,rtibbles/kolibri,learningequality/kolibri,MingDai/kolibri,DXCanas/kolibri,DXCanas/kolibri,MingDai/kolibri,jayoshih/kolibri,christianmemije/kolibri,learningequality/kolibri,indirectlylit/kolibri,mrpau/kolibri,rtibbles/kolibri,indirectlylit/kolibri,lyw07/kolibri,aronasorman/kolibri,MingDai/kolibri,aronasorman/kolibri,jonboiser/kolibri,christianmemije/kolibri,lyw07/kolibri,rtibbles/kolibri,mrpau/kolibri,benjaoming/kolibri,christianmemije/kolibri,rtibbles/kolibri,MingDai/kolibri,benjaoming/kolibri,learningequality/kolibri,lyw07/kolibri,jayoshih/kolibri,aronasorman/kolibri,benjaoming/kolibri,jonboiser/kolibri,mrpau/kolibri,benjaoming/kolibri,jonboiser/kolibri,indirectlylit/kolibri,mrpau/kolibri,DXCanas/kolibri,lyw07/kolibri,aronasorman/kolibri