[TICKLITE-4] Dukascopy feed doesn't dl zero length files

[admin]

At the moment, the system intentionally does not download zero length files as this may be caused by various reasons such as lost internet connection, out of dis space, program crash and so forth.
This is despite Dukascopy actually having zero-length files in their system.
We should try to cater for both - automatically try re-download zero length files but ignore for weekends.

[admin]

** Now fixed in v0.2