URI_templates can't model Voyager PWS lowrate files

[jbfaden]

I can't seem to figure out how I would model the Voyager PWS files. They are in

/opt/project/voyager/data/FULL1/T7901_04
/opt/project/voyager/data/FULL1/T7905_08
/opt/project/voyager/data/FULL1/T7909_12

where 7901 is Jan 1979, and 04 refers to April which is inclusive.