Hardcoded angular range

[wjp]

flexDATA's flexray metadata parsing functions currently seem to have a hardcoded angular range of a full circle, instead of getting this from the metadata.

The new 'Acquisition settings XRE.txt' metadata file has a setting 'projs_per_360' that looks like it might be the most reliable value to use for this. We'd have to switch to preferring that file over 'scan settings.txt' if we want to use that, though.