Fix #96, use non-designated initializer for command header

[jphickey]

Checklist (Please check before submitting)

• I reviewed the Contributing Guide.
• I signed and emailed the appropriate Contributor License Agreement to GSFC-SoftwareRelease@mail.nasa.gov and copied cfs-program@lists.nasa.gov.

Describe the contribution
Do not assume specific member names on structs that are not directly part of the HS app itself.

Fixes #96

Testing performed
Build HS MAT table in both environments

Expected behavior changes
Better source compatibility, no difference in output

System(s) tested on
Debian

Contributor Info - All information REQUIRED for consideration of pull request
Joseph Hickey, Vantage Systems, Inc.