filewriter: swapping data and reset frames in SHM
filewriter: swapping data and reset frames in SHM

Although the reset frame arrives first on the NIC, it is stored in the latter half of the SHM frame buffer.

This closes #24

percival-detector/odin-data,percival-detector/odin-data,odin-detector/odin-data,odin-detector/odin-data,percival-detector/odin-data,percival-detector/odin-data,percival-detector/odin-data,percival-detector/odin-data,odin-detector/odin-data,odin-detector/odin-data,odin-detector/odin-data,odin-detector/odin-data,odin-detector/odin-data,percival-detector/odin-data