ENH: Add GUVI model boundaries

[aburrell]

Is your feature request related to a problem? Please describe.
The GUVI model data is available for specific times in various files on CDAWeb (GUVI and SSUSI).

Describe the solution you'd like
Write a module to extract the necessary model data from these files using pysatNASA (pysat/pysatNASA#148) and use it as OCBs and/or EABs.

Describe alternatives you've considered
Additionally, it would be useful to create fits for the data in the GUVI and SSUSI files.

Additional context
This is not as elegant as running the GUVI model, but I don't have access to it.