Filewriter: decide where histogramming needs to occur

[rerpha]

Histogram mode files are looking like they are a requirement for HRPD-X.

We need to decide at what point in the pipeline:
A) TCBs are actually specified for a histogram
B) A histogram file is created

We may be able to do this after and event mode file is created, ie. by the filewriter, using a service like the FIA. Alternatively we could do it in the filewriter.

The streaming hardware does not currently have the capability to stream histograms so this should not be a consideration. It also becomes more of a challenge for propagating TCBs.

[Tom-Willemsen]

I feel this is best considered alongside filewriter requirements gathering/design work.