Allow the offline workflow to deal with blind injection sets

[GarethCabournDavies]

The current offline workflow requires an injection file. So far as I can tell after being read in by the strain module in the inspiral jobs, this is then only used later in the hdfinjfind and after.

We should be able to use frames from a cache which have injections, but unknown injections, with a background from the full data analysis.

I think this could be set by having an injection-type = blind, or something similar in the workflow config. The statmap files can then be made as they would for injections using the statmap_inj executable, but then presented in the same way as the open box results in the results pages

[GarethCabournDavies]

This should be fixed by #4360